OzVMX Forum
Clubroom => Tech Talk => Topic started by: bigk on October 24, 2016, 04:24:18 pm
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Need some ideas from the brains trust please.
I have a WR430 Husky which has had a complete engine build (rod, bearings, seal, piston etc), done may & nothing is different to any of the others. The bike loads up & won't run with the fuel tap turned on. Turn the fuel tap off & as it leans out it runs clean until it runs out of fuel. If I crack the fuel tap (even 1/4 open), the bike immediately begins to load up again. It used a litre of fuel in about 5 mins of static running, most of it out of the exhaust pipe. Standard 38mm Mikuni with standard jetting for the model.
I have checked, the needle & seat, floats, reeds, air cleaner with nothing out of the ordinary or obvious. I have tried a second carby which I know for certain is good with the same result. So the bike gets too much fuel or not enough air, but I can't see why either should be happening. Anyone experienced this or have any ideas on what is happening?
Cheers,
K
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I would have thought float level, leaking float valve?? but you have tried that.
Is it a after market fuel tap?..maybe its too much flow?
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Is it a reed-valve engine?
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Could both carbs have too high float level?
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Not many things to go rsup in a mic and im sure youve had a look but maybe check and see if there has been a rookie error. Missing washer under the jet or seat. needle in upside down , that sort of thing. Im assuming you can start the big girl okay with that shark hook that they call a kick starter so your on the right track of air or fuel. Could try when its running, spraying crank seal and intake tract to see if the revs change to indicate an air leak. Also check the overflow tube to see if she is dribbling. if the tube is located on the base of the bowl, raising it vertical will give you a ballpark idea of the actual fuel level. if its higher than where you think it should be then issue is between the tube and the needle and seat.
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Tried pretty much all of that & yes it's a reed engine John. The second carb came straight of a good running bike, same make & similar capacity, carb should have worked without an issue if it was a carb problem. It's bound to be something so simple, it's stupid but it has me & everyone I've talked to about it stumped.
K
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Also check the overflow tube to see if she is dribbling. if the tube is located on the base of the bowl, raising it vertical will give you a ballpark idea of the actual fuel level. if its higher than where you think it should be then issue is between the tube and the needle and seat.
Fuel will only run out of that overflow tube(connected to the bottom of the bowl) when the level exceeds desired norm and reaches the top of this brass overflow tube
(http://i677.photobucket.com/albums/vv132/mc125mick/20161024_192339_zpskqujulzx.jpg~original)
If you really want to witness fuel bowl level when static or engine running?
You first have to remove that brass tube. Then and only then will the clear tube display an accurate fuel level when raised up vertically.
Sacrifice a bowl. Call it workshop equipment.
Remove the plastic bag from the new air element?
Rag from air boot? Just being a SA now ;D ::)
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Tricky one that, the ignition & timing all good? Blocked exhaust? Correct piston & top end? Sounds like the fuel is getting in but not being burnt properly or escaping out the exhaust before being burnt, Or forked if i know ;)
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5 minutes a litre seems excessive, has to be a carb fault of some form.
When you tried the other carb did you have access to the tank as well, trying a different tank would eliminate the tap flowing too much and overpowering the float valve as a reason
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Fuel will only run out of that overflow tube(connected to the bottom of the bowl) when the level exceeds desired norm and reaches the top of this brass overflow tube.If you really want to witness fuel bowl level when static or engine running?
You first have to remove that brass tube. Then and only then will the clear tube display an accurate fuel level when raised up vertically.
Sacrifice a bowl. Call it workshop equipment.
true mick , if you can see it that would point to a pressurised fuel tank/blocked breather/ faulty needleseat. being as it does it on both carbs Im leaning to it not being a carb issue now. Its had new seals so perhaps a lip isnt seated
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Tricky one that, the ignition & timing all good? Blocked exhaust? Correct piston & top end? Sounds like the fuel is getting in but not being burnt properly or escaping out the exhaust before being burnt, Or forked if i know ;)
Yeap, forked if I know too ;D ;D
If you were drinking when you did? give up drinking and start the rebuild from scratch again.
I have stopped drinking completely, everything is different now.
I used to spend at least an hour everyday looking for my keys and wallet,
Got it down to 55minutes now :)
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That pressurized thing would be worth eliminating Pokey.
Actually, I was giving a friend a hand on a 430 husky with a Mikuni, only 2 or 3 months ago.
Ignition problem.
After we tried to sort it again a few days latter, it was pissing fuel out of the Mikuni for apparently no reason, I abandoned it then and went home and left it to the owner ;D
I should have popped the cap Pokey ::) ;D
Uuumh, non vented cap on a non vented tank?
Bike didn't come from Newcastle recently, did it?
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it appears the carb isn't the issue if the 400 carb does the same thing. exhaust or muffler? can you swap the 400 ign system?
reeds arnt stuck open or shut?
the turning of the fuel is the clue and momentary clean running
the carb to filter boot isn't sucking in and blocking air?
just musing.... but if it runs clean on leaning mix there is too much fuel in the motor. we know the carb aint doing it.... thus there is not enough air getting in per firing stroke....air filter but you've checked it...airboot? no loose flap sucking across the carb. airbox is pretty open so should be visible...air cant get out..blocked pipe? will it idle? but not take any throttle?? wasp nest in the muffler??wack a stick in it to check...
if it was electrical, turning the fuel on or off shouldn't affect it.
this is a good one!
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yeah mick that vent issue has got me twice before (im a slow learner). It usually makes them starve for fuel but depending on the temp of the tank they can build up pressure too. worth as you say, Popping the cap to eliminate that possibility. that fuel usage as one of the guys mentioned is of a concern as it does seem excessive. This is going to be an interesting thread i think.
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What about the little plate doovy that goes under the big throttle slide return spring and holds the slide needle in position?
Is it there doing its thing?
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yeah mick that vent issue has got me twice before (im a slow learner). It usually makes them starve for fuel but depending on the temp of the tank they can build up pressure too. worth as you say, Popping the cap to eliminate that possibility. that fuel usage as one of the guys mentioned is of a concern as it does seem excessive. This is going to be an interesting thread i think.
Yeah Pokey, I think a non vented cap on a non vented tank getting the shit shaken out of it with the kick start action, might be like every Jerry can I have every opened ;D
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What about the little plate doovy that goes under the big throttle slide return spring and holds the slide needle in position?
Is it there doing its thing?
My money is on this or something to do with needle/slide.
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did you try the 430 carb on the good running 400 to be sure it's ok?you can make a bike running level gauge out of the bowl drain cap and tap it for a 90 degree bend.when I rebored my ts185A I put a yz125 32mm carb on it to match the port job I gave it and it ran like crap loading up no matter where I adjusted the float level and it only ran good when the bowl was nearly empty and upon checking the needle/needle jet I could see the wear and why it wouldnt seal off when on the pilot jet.when I put the std carb back on the bike idled like it did before
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What about the little plate doovy that goes under the big throttle slide return spring and holds the slide needle in position?
Is it there doing its thing?
My money is on this or something to do with needle/slide.
Me three. Was the whole carb swapped or just the bottom half with the cap, slide, needle etc from the original carb used?
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my nephew had a wr400 yammie that used to run for 30 mins then stop...just enough time for him to get out to the "back country" on the property he was working at. it would not start for 20 - 30 mins then it would do the same... it was stripped to the crankshaft twice with no result over a year. he bought it home and I took it for a spin. no probs...rode it for an hour without a hiccup. then....decided to slip home via the road...15 mins and bwuaaaaahahh it stopped?? ( just near a mates place) so had a coffee and came out and kicked it and it went?? so riding home quietly I noticed it was not giving me "main jet flow" skidded to a stop, opened the tank cap and swoooosh...sucked whole lot of air in. checked the breather ... ball bearing jammed in it.
Apparently some ones chookshed was burned down later that nite... ;D
wait! moral...blocked cap seemed to reduce flow more than push it but I can see how fresh fuel in a sealed tank could load the needle and seat.
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This might sound stupid but pull the head off and see if the piston is in the right way.
A mate had an '80's model CR125 that sounded similar in many ways. Turns out that he did the simplest mistake in a rush. It ran but loaded up. Had us all scratching our head until in pure frustration he pulled it down only to fine the piston in the wrong way.
Peter B
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All good thoughts thanks, however I have checked all of that including if the piton is in backwards (it's not), it's doing my head in. The bike has great spark, the timing is correct, it starts from the kicker (albeit with the throttle held wide open), so it doesn't seem electrical, but could it be an ignition issue?
K
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Need some ideas from the brains trust please.
I have a WR430 Husky which has had a complete engine build (rod, bearings, seal, piston etc), done may & nothing is different to any of the others. The bike loads up & won't run with the fuel tap turned on. Turn the fuel tap off & as it leans out it runs clean until it runs out of fuel. If I crack the fuel tap (even 1/4 open), the bike immediately begins to load up again. It used a litre of fuel in about 5 mins of static running, most of it out of the exhaust pipe. Standard 38mm Mikuni with standard jetting for the model.
I have checked, the needle & seat, floats, reeds, air cleaner with nothing out of the ordinary or obvious. I have tried a second carby which I know for certain is good with the same result. So the bike gets too much fuel or not enough air, but I can't see why either should be happening. Anyone experienced this or have any ideas on what is happening?
Cheers,
K
Sounds very much like float valve as your doing the job of the float valve with the fuel tap. It may look ok but the head pressure from the fuel is too much for it. It could be too big a size for it also.
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If you want to rule out ignition from the equation?
Strobe light it to check its consistency whilst running.
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Other than that. Matt's idea about the hose from that threaded bung in the bottom is sound. At least you will know wether a varying fuel level is in or out.
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When you swapped the carbs, did you also change the needle & slide? I think someone mentioned the needle sliding up in the slide (not secured down).
Failing that, have you run it with the airfilter element out? Maybe the pores are not flowing enough air from being cleaned in wrong solvent?
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You didnt answer if the fuel tap was standard? Iv had an issue before with a oversize fuel tap. The standard carb couldnt stop the extra pressure.
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Take the carb off but keep attached to fuel line, turn fuel on and see what happens..
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you have my attention;
can you run the carbs on another bike just to cross check
place another tank onto it ( I use an old lawn mower tank for bench testing stuff )
maybe a bit of this and a bit of that ie slightly high float level with needle and seat sticking mid drift, needle jet, jet needle is all that ok as in is it locked down with washer, clip, spring (but on both carbs)???
good luck
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Check the reeds out?
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Come on Mick, you've got me in suspense, what was it?
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Come on Mick, you've got me in suspense, what was it?
Yer what he said lol
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You didnt answer if the fuel tap was standard? Iv had an issue before with a oversize fuel tap. The standard carb couldnt stop the extra pressure.
How does a larger tap cause extra pressure? Pressure in this instance is purely a function of hieght.
A too small tap can cause starvation naturally
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You didnt answer if the fuel tap was standard? Iv had an issue before with a oversize fuel tap. The standard carb couldnt stop the extra pressure.
How does a larger tap cause extra pressure? Pressure is purely a function of hieght
Quite right HeavenVMX. Head or rather verticle head is a measure of the height of liquid above a set point. No matter how wide it is the actual pressure will be the same at a given depth.(ocean or bucket its the same) With that said, friction in a smaller pipe increases thus slowing flow but in the size we are discussing this is negligible and not worthy of calculating.
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Yep realised I needed to qualify my over simplified statement
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Yes, with respect the increase in tap size will not effect static head pressure at the float needle valve, only the available flow.
The two main factors in head pressure calculus are height and Specific Gravity(density) of the fluid in play.
In a vented tank situation the available flow is irrelevant, unless there is a lack of it>then starvation>lean burn on wide open throttle straights and other high demands, dune riding etc.
Back to our all eyes mystery ;D
In regards to
Head or rather verticle head is a measure of the height of liquid above a set point. No matter how wide it is the actual pressure will be the same at a given depth.(ocean or bucket its the same) With that said, friction in a smaller pipe increases thus slowing flow but in the size we are discussing this is negligible and not worthy of calculating.
There are a few miniscule variances not worth calculating eg; Temperature for one,
BUT, one very important factor of calculation is the density(specific gravity) of the liquid in mention.
Pure unadulterated H2O weighs the "basis of the entire metric system" ie; 1 Kilogram per liter.
The old super grade came in at close to .75 kg per liter(fuel floats on water because its lighter gig).
0.8 of a kilogram per liter is a very close mean for all intents and purposes for our fuel/oil two smoker blends,,,,
So the head pressure outcome at the float needle valve seat is actually 20% less if considering mixed fuel/oil of a 2T than if it were a calculation factored from say the SG of water instead.
If considering the pressure at the float needle seat of my 78 Magnum (from calculation, not pressure gauge),
The outcome of a tank with only 5mm from empty is 0.0192 bar(only 0.278473 of one PSI.)
When my tank is full, the level is 420mm above the Float needle valve seat.
Pressure of water at a 1 meter high head is 0.1 bar
But we are talking fuel/oil mix so multiply 0.1 bar by 0.8 for fuel/oil mix = 0.08 bar
Now multiply that by a full tank head above valve height of 0.420 of a meter = 0.0336 Bar(0.487328 P.S.I.) of pressure at my Float needle seat.
So that is in a static scenario with vented tank full at 420mm height above valve, Less than half of one PSI.
I would love to know the pressure of a trailered shaken Jerry can in the sun? :-[ ::) :o
As our resident rock hugger has noted
my nephew had a wr400 yammie that used to run for 30 mins then stop... checked the breather ... ball bearing jammed in it. Apparently some ones chookshed was burned down later that nite... ;D
So vibration agitation(whatever) of a non vented tank of fuel will produce enough vapour pressure to keep the bike in giddy up mode for 30 minutes?
I also wonder how much a sound float needle valve can handle?
Those vacuum pulse diaphragm pumps on Out Boards are rated at 3.5 to 4 PSI(I have tested many of them).
I wonder how much pressure it would take to show up fault in a Mikuni VM38?
Anyhow just all shit hypos'
Come on Mick,
Hey remember when Ji Gantor got the answer for that "what steel are Maico frames made of" but then went boating for the weekend and kept us on suspenders, instead of telling us the answer ;D
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Standard Cawi fuel cap for Husky's is identical to look at regardless of whether it is the vented or non vented type
(http://i677.photobucket.com/albums/vv132/mc125mick/s-l1600%203_zpsqtrhv5su.jpg)
It would be an easy oversight for any owner to neglect to check on when purchasing a cap of say ebay?
But I think maybe Mick has already responded to that as a "no" earlier in the thread,,,,
So I am just saying OK :)
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Yep half a PSI maximum ( i will trust your math Mick as Ive had a scotch and have shoes on so counting isnt going to happen) ;D and seeing as the carb was designed to hold back a tank full of full of fuel I dont think normal head pressure is the answer no matter what size or material the tube used. the theory of additional pressure would be valid. had a smilar problem with a radiator cap causing issues that some fool :-[ bought instead of a return type. Its good to vent.
What we have is the fact its a thirsty b of a thing.
Seals have been replaced recently but we have no mention of plug analysis (possible leak but it runs ok when fuel metered but excessive fuel consumption points to carburation error)
carbs have been changed for the same result which would "normally" rule out carb
We dont know if the "entire" carb has been replaced (Needle keeper plate/ needle clip incorrectly installed?)
metering with fuel tap suggests carb is not metering fuel at all. (needle keeper plate/ Dodgy needle and seat/ excess pressure on needle and seat)
This leaves us with probable incorrectly installed/ faulty carb components. being as i doubt the needle and seat was changed in the carb swap Its most likely an incorrectly installed needle .
Im hanging to know what it is. Someone should run a book on this one . I wonder if anyone will guess Missing golf ball rolling around in the chamber?
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Gee weez mick mixing metric, imperial plus yank units of measure all in the one algorithm bad form man :P
But the outcome is still the same that having a larger tap outlet would not increase pressure to the carbie in a vented tank, regardless of specific gravity. In this instance SG can be considered a constant anyway.
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hey pokey, I was at the shop when mick swapped carbs, pretty sure he had the whole shebang going across to the 430. this is a weird one, mick has only to swap electrix to rule everything out. it will be something innocuous, but he has been thru the wiring, looked inside engine and exhaust to check the basics pretty much covered it all except a replacement stator / flywheel.
I had a mate who was a mr Mc Hanic years ago and his datto 180 sss was playing up. running on idle, flat spots etc but weirdest of all at 6K it would slow suddenly, ping like crazy and blow a huuuge cloud of blue smoke out the back. :o he recoed the carbs, checked and checked...took it to a carb expert, no luck there...then one Saturday morning, while the carb man was fiddling with it, a local identity who was standing by, Melbourne stubby in hand (9.30 am) suddenly leans in and says "that little hose has a split in it"
the sump to carb "pcv hose" had a split and at high revs would venturi sump oil direct to the manifold. $3.50 later all fixed. total bill over $800
just sayin, you've got to look outside the box sometimes
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longshot....
similar thing on my 74 Husky 450 a few years ago, changed from the Bing over to a new Mikuni
it loaded up and would foul itself up with fuel within a couple of minutes
was just rideable if you were wide open throttle but even then it didn't last long
turned out that when I shortened the manifold and used a piece of old radiator hose as a joiner I had not separated the carburettor (so that it was a little bit isolated) and it was touching the manifold and was shaking/vibrating so much so that the needle and seat would not stay closed
not enough "leverage" on the float linkages to keep the needle closed with all the vibration, moved the carby back about a centimetre and all was good but it still occasionally had the problem so I rubber mounted the air box/filter and have not had a problem since.
and now I recall that my brother the engineer brains of the family said it was all to do with harmonics - just a particular combination
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Interesting comment there, my CZ is doing something similar through the mid range since I changed to a reed valve top end & I found the carb was possibly touching the aluminum airbox
I've shortened the carb some more but haven't had a chance to test it out & won't get to until next weekend
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So entire carb has been changed? Whale oil Beef Hooked.
Dodgy CDI. Thats all i got left as Im fairly sure big k wouldnt have made a rookie error with fitting the cable/needle plate
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Makes perfect sense pokey, based on the fact that 95% of carby problems are electrical.
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its got me rereading Graham Bell and trust me you don't need to be a rooky to have carby problems
we had this XR75 once had all the poop jets neddles carby kit etc could not stop it blubbering ok Ive lost my carby mojo got old mate RAT the carby genius (rip) he laughed just something simple wont take much they are pretty simple!!!
Any who he gave up after playing with it way to long
so another mate no slauch in the carby tuning side of things was sure he find the problem, is the carby worn give me a look
Any who he gives up after playing with it way to long
So went to mates place swapped carby's with his kids XR75 mine ran just fine (real nice) and here is the best bit so did his with my blubbering mess on it, ok problem fixed swapped it back to mine a blubbering mess again
is this the devils work, aliens or poltergeist
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Shed gremlin
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the suspense is killing me!
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Sorry guy's, I cracked it & walked away (for some time), fairly sure I've solved the issue but haven't actually started the bike yet. Will report once I fire her up again. I'll attempt to get it done this week before I get both my hips replaced on this coming Saturday, otherwise I guess it will be a week or two after that (when I find someone else to kick it over).
K
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Big K you sound like you need to make one of Lozza's famous 9inch angle grinder starters and save those new hip joints from wearing out
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he has been too busy winning another bloody medal and the pan pacs masters..... ;D
https://youtu.be/H_1m-d0FOXI
he might be in this vid im not sure...
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he has been too busy winning another bloody medal and the pan pacs masters..... ;D
https://youtu.be/H_1m-d0FOXI
he might be in this vid im not sure...
Bloody good work! And YAY new hips, old mate Barry from RCB got his done less than 12 months ago and is luving it!
all the best and the blinking carb can wait its turn
cheers pete