OzVMX Forum
Clubroom => Tech Talk => Topic started by: frostype400 on July 31, 2017, 10:14:28 PM
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Well taking a look at my pe400 after it decided to stop on the weekend I thought my flywheel may have slipped as it had before but no it has lost nearly all compression big time so I pulled the top end down.
so straight away noticed scoring front and rear of cylinder and I didn't take a picture but it looks like the piston ring locating pin is gone so I am assuming that's what has caused the scoring with the ring then having to much end gap?
looking for thoughts will the cylinder need rebore or be ok running the same size piston and what should I look for to make sure it doesn't happen again, thanks Michael.
(https://image.ibb.co/j41vN5/pe400_cylinder_1.jpg)
(https://image.ibb.co/e8eUFQ/pe400_cylinder_2.jpg)
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Looks like its seized,something big pe's like to do!can you put some pics of the piston as well
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After reading your "What did i stuff up here" story
its questionable that the ring pin has gone, if it was not present at all the ring would have rotated on the piston and the ring would catch in one of the ports & major damage occurs ! prior to seizing like this.
or the ring may of claimed over the ring pin as the ring & bore would have to be very very worn.
Appears to more like a heat issue, whats the top of the piston crown look like?
Was the bike pinging, its a death rattle under high load.
Did it blow at high ground speed ?
Is the carby clean, no blocked jets? is there water in the fuel bowl, main jets may not pass water, surface tension is the issue!
Was the bike running a high idle speed after a run / coming to a dead stop, then returning to slow idle after a short period or even stalling, this is likely a crank seal & or air leak at base gasket or intake manifold.
Not that this bike was likely blowning massive smoke ( bore looks very dry & lack on carbon deposits ), but if it was the primary drive side crank seal leaking, drawing trans oil and burning it, which once the seal runs dry, it also sucks air ( lean) what the trans oil comsumption like?
Husky mag motors do this ask "Tossa" mag crank case bikes that have had water sitting in them at some stage equals shitty cases.
If the piston crown is damage in the centre like a hole is forming, its likely the heat range of the plug to hot and lean mixture.
Comp bikes "NO" 7 or 8 NGK hot range plugs , 9s in air cooled bikes & 10s in water cooled, if it needs a 8 or less to run dry its to rich, like wise other brands near coldest plug or coldest only.
If the piston crown has alloy splatter over its detination, poor timing.
If the piston crown is blown away at the front / exhaust port its pilot jet is to small, the bike also would of been pushing your though the corner like its lean. but probably returned to idle well prior to failure.
If the intake skirt of the piston has seize marks its lack of oil. wrong oil ratio !
If both sides of skirts of the piston have seize marks it could have cold seized ( not warning up the bike and thrashing it from stone cold )
Rings end gap that is to close ( fresh rebored motors ), also cause engine seizures, more so at the exhaust brigde in the cylinder & piston in that area. not that this is a bridge port motor.
Was the bike kicking back though the kick starter, if so its to far advanced timing. also leans out the bike and run hot.
Bikes that are hard to start may have low float level, this also leans out the pilot circuit, guys that have leaking float needle valves that bend the float tab are also making they bike hard to start. low fuel level equals lean pilot jet.
Just a few things i have seen, found or experienced on my own bikes and clients over the years.
I have found as main jets and jetting goes, engine temp drops as the jet is close to been correct, wrong jet high temp. as the engine gets close to the correct jet the engine cyl head temp drops, if it begins to rise again its getting the wrong way, either rich or lean!
Capacity has also an effect on air cooled cylinder head temp, small 125cc around 85-95 deg, 250cc 120-140 deg, 500cc very hot, close to 190 deg, on this bike its one jet size out and blows passed 205 deg, should be running methanol, all temp measured three laps at Narrogin.
Regards Gibbsy
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Thanks guys I will get some pics of the piston as well and it happened at fairly high speed over shot Where I was supposed to turn and then it died when I was going back through the gears.
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What oil/fuel ratio are you using and the type of oil?
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32:1 Penrite oil.
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Damn..you mentioned flywheel spinning...was that thought from an aftermarket ignition..?
That pricked my ears because I have fresh 81-400 motor & about to purchase a dynamo 12v..
Hope you find the issue :)
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were you at harrow? the ground there is very boggy and puts enourmous loads on a/c bikes. too lean at all in any circuit will become critical on those boggy steep uphills, real seizure territory.
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Yeah I was at harrow I was on a road when it happened but flywheel hadn't moved yes it was a powerdynamo one 12v I'm going to take it off and lap the crankshaft and flywheel with valve grind paste I had a mate put the flywheel on after it span but not sure if he did that so I will do it as precaution any way.
I was way to rich early on and couldn't rev out played with the carb and got it to rev out I might go back to 20:1 though as that's what they ran stock
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i rekon 30 - 40 to 1 is fine, oils are pretty good, i suspect timing / jetting has been your problem. as an example although my 400 is water cooled, i jetted it in 2011, got it just nice and havent touched it once. if your still playing at harrow you will have trouble as the country is hard on jetting and timing errors. also with the A/c bikes, the mud increases your engine temps considerably and you could also have an air leak. harrow will find that for you. as you probably noticed, its like riding with the rear brake stuck half on.
clean it up, new slug (if the bore is ok..) and run it in well at 20:1 then drop the mix out a bit and work on jetting it so its crisp and nice through the range. with an a/c i would make the needle jet slightly rich if possible just so its spluttering a bit at even throttle but not dragging the bike as you open up.
good luck
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Its just got very hot, more oil (castor/synthetic) will fix that.
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hi speed,overshot,bang down thru the box,shutting the throttle,big bore motor = no cooling coming in,look at the bore,classic thrust fore /aft seizure,like 80-85 says richen n/j, :P
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My brother inlaw pe400, also fresh motor 0.50 over boyesen reeds, 175 ignition, fouling plugs on penrite full synthetic..I'm running silkolene full synthetic 30:1 no issues at all...we did the builds together. Food for thought.
I usually lap a flywheel in twice,,again after a good run..
Ps, I just paid for a dynamo.
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I'll get a photo of the piston in a sec just heading up the shed will I be ok to just replace with new piston and rings same size?
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I was wrong ring locater is still intact so possibly may only need a new ring?
(https://image.ibb.co/eU7CkQ/IMG_0119.jpg)
(https://image.ibb.co/eHOUX5/IMG_0125.jpg)
(https://image.ibb.co/eLsdQQ/IMG_0126.jpg)
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another tip frosty ;D dont go to harrow with a fresh engine.... get at least two tanks of fuel on it or more i rekon...used to see this at the bp sea lake rally back in the 80's. half the field would be once a year racers and half would "do up the bike"just before the event. that half only made it half way down the first open salt flat ::)
if you sand the alloy off the barrell or get a light hone, it should clean up for a new ring and a bit of a wet and dry polish on the piston. check the gap is ok. put it back together and jet it up a tad and get a tank or more in general light running on it just easing into the band at 1/2 or more throttle. after say two tanks start giving it a bit more letting it work up into the band a bit more. now you can look at cleaning the jetting up by leaning the main (if its blubbing a bit or dragging on full throttle) then look at the 1/4 to 1/2 throttle area ( Needle jet) and feel how its going as you roll the throttle thru that range...if it drags on opening the throttle then takes off on the main jet, teh needle is rich so drop it a notch see how it goes. if its sharp and responsive like the fuel is running out your too lean, let more juice thru. look for the middle of that range.
the pilot should see you needing choke to start and a nice idle with teh air screw 1.5 turns out. if the air screw is unresponsive then the pilot is wrong. (or you have an air leak) check your manifold isnt split, they can hide in the ridge lines and open up when you hit a bump. i have fallen for that chestnut before.
a massive ping and over rev when you land from a jump is also a giveaway.
hope this helps...PS There are much better people than me at jetting also is the muffler clean and well packed??
cheers
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Going on how scuffed the piston is both front & rear I'd replace it, will rattle otherwise.
Can you feel any of the scratches on the bore with a fingernail, that will be the deciding factor on whether a quick hone is all that is needed for the cylinder
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I had a 250 that looked similar. To get the most out of it I cleaned it up respectfully & did the main seals. It ran strong for half a day..I'd take piston off & put it on the bench with barrel & some measuring tools ;)
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could the pipe be helping with this problem, restrictive muffler throwing heat back into the head
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Air cooled bikes = mineral oil
I will never put anything but mineral oil in my old bikes.
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if you sand the alloy off the barrell or get a light hone, it should clean up for a new ring and a bit of a wet and dry polish on the piston.
Can't sand aluminium off a bore needs to be 'fizzled' off with hydrochoric acid. The piston is forked it trapped the ring . I was wrong ring locater is still intact so possibly may only need a new ring?
(https://image.ibb.co/eU7CkQ/IMG_0119.jpg)
(https://image.ibb.co/eHOUX5/IMG_0125.jpg)
(https://image.ibb.co/eLsdQQ/IMG_0126.jpg)
Its not a lean seizure its from lack of lubrication as above mineral oil will stop lubricating with enough heat, new ring new piston. Run it in by idling on the stand for 10 min then 10min cool down and then nail it pussy footing round does the piston no favours
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What was piston to bore clearance? Looks to me like it was a bit on the tight side. I have honed cylinders that looked like that out to the correct clearance and given them new pistons with good success.
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Thanks guys I'll order another piston and get the aluminium off the cylinder I'm also going to do some plug chops when I get the chance and look at getting my jetting spot on pipe and muffler is new and unrestrictive I was happy with how the bike handled my forks and shocks worked a treat I was a bit rushed in preparing for the event so I'll make sure it's well and truely sorted for next time.
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I'm feeling your pain Frosty. I've now seized our 1982 WR430 Husky 3 farken times at harrow. Over 3 years :'(
The first time was with a new Wossner piston and running at 40:1 with Motorex Oil. It seized on the first big open strait.
Second time it had another new Wossner piston with slightly bigger clearances and runing at 25:1 on Motorex and seized on the track to the fuel dump.
This year we were out to 0.005" piston to bore clearance as it's on 3rd oversize and there's no fourth oversize. Also worked out it had a stuffed crank seal on the fly wheel side :'( replaced that, we thought the seal was the reason for seizing it the previous 2 times.
We ran it in at 25:1 on Motul 800 this time and had a temperature prob in the exhaust to read how hot the gas temps were getting.
It was working well and I put about 60km in on it running it in. Getting it hot switch it off and cool right down, did that 3 times not even riding it.
Than road it for 5-10 minutes at a time short shifting it for 30km.
We did the practice loop on the Saturday at Harrow and it wouldn't rev out. So went playing with the needle and main jet.
With a 460 main (used to run a 440) and the needle on the bottom clip (Also changed the needle, I can't remember the needle that was in it but i was running a thinner needle to keep the mid throttle gas temps down) and it went the best yet.
I than got greedy and thought I'd try 30:1 and went for a ride and it felt even better up top. I was riding back to the camp and thought I'd check that it wasn't too hot at half throttle and glanced at the gas temp and saw 600 degrees celsius. And it seized again :'(
I pulled the exhaust pipe off to have a look in the barrel and it's seized the inlet side of the piston.
Which by rights is the cool side of the piston.
So everyone's theory that the fuel has more of a cooling effect than the oil isn't correct as the engine didn't seize at 25:1 but did at 30:1 with a bigger main jet.
Anyway after that everyone at Harrow has a different theory why it seized-
1- Piston to bore clearance was too much not allowing the piston to transfer it's heat to the barrel and cool?
2- To bigger squish height, creating extra heat above the piston. It has been running a copper ring head gasket for years on Mahle Pistons and never gave any trouble.
3- Something's wrong with the ignition timing or curve and it's running to hot with retarded ignition timing.
4- It has another vacuum/crank case leak somewhere?
Sorry to hijack your thread but I don't want you to be in the same situation we are in, 3 years in a row.
Harrow is a very hard environment on old bikes and every year we seem to be out of time and throwing our bike together last minute.
So our plan is to get the barrel re-sleeved back to a standard piston and correct clearances.
Get the squish height right.
Get the ignition curve checked.
Pressure test the crank case to 10PSI and make sure there's no leaks.
And than spend a lot of time running it in and than even more time getting the jetting correct which might be a lot easier on a dyno as after seizing it at half throttle I don't believe anyone can work out how hot the engine would be running at that speed and load by just reading the spark plug colour.
It happened that quickly.
Cheers Ryan.
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I'm interested to know what piston your using (single ring) if you don't mind sharing..?
Cheers.
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I have seen this more than few times , You have to use an oil with wick action ( to help cooling ) if you choose not to then when you really labour the engine In mud/sand this can be the result. Most modern oils dont have wick action.
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I'm interested to know what piston your using (single ring) if you don't mind sharing..?
Cheers.
Markings on top & lack of teflon coated skirt would suggest Wiseco
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KX500 piston mod I keep hearing about..?
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I'm interested to know what piston your using (single ring) if you don't mind sharing..?
Cheers.
The Wossner Piston is single ring with Teflon coated skirts.
I have seen this more than few times , You have to use an oil with wick action ( to help cooling ) if you choose not to then when you really labour the engine In mud/sand this can be the result. Most modern oils dont have wick action.
I'm starting to wonder the same that the Motul 800 isn't up to it? But a lot of people I've talked to run there air cooled big bore 2 strokes on it up to 40:1?
When I was racing my 1974 CR125 in the 1990's it had a problem seizing the piston on the exhaust side. The fix then was to get the piston Teflon coated and we ran Silkolene Pro Comp 2 I think it was? In a metal tin.
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i used silkolene pro comp years ago and it was good. that crank pressure test will be interesting.... i wondered why you were on a pe :D
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This is only my ideas and opinion and years of experience. And thankfully some real testing and shit.
Air cooled engines need to transfer heat between the piston and cylinder ( this is called wick action ) Water cooled bikes dont have this issues. The idea is un-burnt oil and oil itself moves heat between the piston top and the cylinder, new oils, synthetic oil burn to cleanly to do this , the piston over heats in tough going as shown in the photo's. You actually need the old smelly oil to keep your bike running well. You cant transfer heat thou an air cap , new oil burns so cleanly they leave an air cap , old mineral oil dose not.
Sad but true you are better off running super TT castrol than the latest Moterx Oil. But please ignore this advice I will simply ride past when your bike is locked solid , it is much easier for me to pass :-)
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It's not a pe piston it's a maico 490 piston my crank isn't standard and has a different rod in it and you can probably make out the barrel spacer in the pics so it's a pe 400 cylinder yes but the rest is all different.
I will order another one you live and learn with these type of things it didn't really even upset me I was only spewing I didn't catch up to ride with my mates in front of me and I could see how it could cause some havoc being so wet bikes under a lot of load and I got a bit carried away trying to see what it could do and it was flying when it seized.
May not have ran to well for me but it handled and looked good at least.
(https://image.ibb.co/hb23AQ/IMG_0117.jpg)
I will probably run mineral oil from now on and I am going to start at 20:1 the oil I was using I noticed it wasn't making much blue smoke but I just put it down to being a fresh engine.
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Two strokes always run best before they seize Frosty ;D
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Me being stuck in a creek Frosty meant i didnt get to see you get out of the parce ferme in the mighty XB...there was some money on you being stuck ;)...how did you go? ;D
ive got to sort of agree with Slaky on the Mineral oil and a/c engines, it has a ring of plausible about it. (face it, who wants to cook an engine to test the theory??)
ive had great success running synths at high ratios (i.e no problems at all) but always in watercoolers..I ran the blower vac and chainsaw on 100 to 1 with no probs but they dont get a deep mud workout like the bikes do...
great looking combo the xb and the PE...i was thinking of putting a towbar on the old monaro and bringing the scooter down on on a trailer...might be a 10 year anniversary project...ill start saving for the petrol 8)
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FWIW.. those pics look like a lean seizure to me..the fuel does the cooling and the oil does the lubricating..too little fuel (too much air) and you end up with a piston that looks like that.. My first response would be to do a leak down test..these bikes are in a lot of the cases 40 years old..or close to it..check the excess air getting in..
40.1 in my old aircooled banger..Motorex full synth..no problems once the air leaks were sorted.. ;D
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In regards to oil. Most will not notice and apart from quicker wear which does not matter a great deal on a bike ridden a few times a year the difference between Mineral and synthetic. It really only came to my attention when I started putting old A grade riders on my bikes. A good friend of mine having similar issues with A grade riders decided to get real data so he welded a heat censor in the header pipe and did back to back testing with fuel and oil and by far the coolest running was with 98 pump fuel and 25 to 1 mineral oil. Try a test, use your fuel you are using now and listen carefully , now do it again with the mixture above , I can hear the difference less rattles.
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dirt track /road racing 20-25 to 1 you are realy reving the motor
and as you will find out frosty oil is cheaper than parts
20 to 1 on methenol ran four years never fouled a plug just re ringed motor and new bearings and seals
jim
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Thanks guys I will get some pics of the piston as well and it happened at fairly high speed over shot Where I was supposed to turn and then it died when I was going back through the gears.
nobody really read this bit apparently ::)
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fairly important im thinking....
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Yeah I did read that but currently have a 400 stripped down now here in front of me I'm more concerned about not seizing...! Good point none the less..Frosty did you just do a fuel stop & forgot the oil in the new lot..???
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No I definitely had all my fuel mixed never got to use my spare fuel any way.
And yeah I got medium stuck ;D I didn't need towing out like my mates in the big dodge setup in the same area I just needed a bit of a push to get going thanks those guys if you are reading.
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Seems that whenever an engine stuffs up everyone wants to jump on the oil ratio bandwagon to justify their cause.
I think it this case though it was most likely something else.
Did you inspect the base gasket for leaks Frosty?
The problem with spacer plates is 2 gaskets increase the risk of a leak, the gaskets can bed down over a few heat cycles and 2 gaskets may be enough to leak whereas one gasket will be fine.
I'm not a fan of using gasket goo on base gaskets but I think in this case it is probably worthwhile.
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Its simple, its becouse all new oils are evil. They are only made for Kawasakies.
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Going to recheck every thing and leak down test etc etc ordered a new piston so I am just waiting now.
Also it doesn't worry me if I am not sure what caused it as long as it doesn't happen to me again.
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Also it doesn't worry me if I am not sure what caused it as long as it doesn't happen to me again.
:o
Ask Dewy, they tried that process and 3 pistons later they realised the main seal was poohed...i would work on making sure you know why it failed otherwise.... "definition of insanity" doing the same thing over and over and over and hoping it will turn out differently ..this time... 8)
leak down test will sort it out for you.
good luck
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"Seems that whenever an engine stuffs up everyone wants to jump on the oil ratio bandwagon to justify their cause."
that is so true ,
I used to believe that using the most expensive 2 stroke oil at exactly the right ratio was critical,
then one day went riding with a mate and he mixed up the fuel for both bikes {air cooled Ossa + Yam IT},
when packing up at the end of the day he realised he had made a mistake and had mixed some Silkolene Fork Oil with the petrol instead of Silkolene 2 Stroke Oil !
both bikes ran perfectly all day on the Fork Oil Premix, maybe we where just lucky or maybe these old engines will tolerate different oils & ratios more than you would think
anyway , just saying , not trying to offend anyone,
has anyone else done anything similar ? or are we the only idiots to have done this
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Joey Dunlop ran out of fuel at the TT and astounded onlookers by draining one fork leg and mixing it with fuel and riding back to the pits. Though riding back to the pits and trail rides are not fanging in sand or mud.
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Team ADB went racing their kdx 200 at 200:1 when they forgot to put oil in the fuel can...no probs.
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Joey Dunlop ran out of fuel at the TT and astounded onlookers by draining one fork leg and mixing it with fuel and riding back to the pits. Though riding back to the pits and trail rides are not fanging in sand or mud.
Good old Joey D--legend. Remember a similar story of someone out trail riding & the thirsty 2stroke ran dry. So pinched some fuel out of his mates economical 4 stroke. Took the tail light lens off & emptied some oil out of the gearbox & mixed it up then carried on to the end.
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When we were young blokes Fino (god bless) had this old TS that had a hole in the box case. He rode it for about a year, In the end he didnt bother toping up the gear oil and never bothered puting any oil at all in the fuel. It ran for a few weekends and still went when he parked it up for the last time. It was a beast.