OzVMX Forum
Marque Remarks => Suzuki => Topic started by: Freakshow on September 10, 2007, 02:48:28 pm
-
Hey all im sure i have asked this in the old forums but i want to revisit it.
MY 74 TM250 has a Muk with a 33mm throat so im assumning its a 32mm, i thought it had a main jet that says 270, but evey time i run it on a big track it dies in the arse like i kicked the choke on until you let it get back on the pipe, worst on long straight tracks, maybe i misread the jet as all my other 250cc (reed valves) run a 270+ i thought this was the same, where the Number is written its been moved by a burr, so maybe it says 210 ? can someone tell me what the standard main is ? and are they or why are the piston port motors on the same cc using less jet ?
got me fcuked, but its all i can think of right now. bloody suzuki will be the death of me - mentally :-\
-
From what I've seen mains on TM250 run #180-#220 with a step of 10 in between, maybe you have an air leak? Are you using the standard airbox? Have a look http://alpha-sports.com/suzuki_parts.htm
-
Your problem will almost certainly be fuel related.Best way to sort the main is to start with a jet you know will be to big. Say 320 and work your way down making plug chops along the way.If you do a chop when it dies what does the plug look like????? What sort of rpm is this happening at?
-
Surely someone can tell me the standard 32mm main jet on a TM250 ?
yes lozz i did the chops but track time is limited i know 300 and 270 is tan, but it only happens at 3/4 throttle and under load, if you free rev its like a chain saw i know that cause when i jet down at the track to the 270 the throttle got stuck wide open, my ears bled.
i think it could be a 210, but i dont want to go that low if its supposed to be around the 270. BUt i have one more chance this weekend to get it right so id like to start close to the target, not 10 chops in. The closer i look the old one looks like the number 210 not 270 . My kindom for a straight answer. what is the original 32mm main jet ! ::)
-
From what I've seen mains on TM250 run 180-220 with a step of 10 in between, maybe you have an air leak? Are you using the standard airbox? Have a look http://alpha-sports.com/suzuki_parts.htm
are yes your right they list all 4 and have the 180-190 as the stock. IM assuming that the standard VM its shipped with was indeed a 32mm Mikuni > ::)
Which would mean im not going totally mental, that would mean it is indead a 210 thats written on it ( mental note buy a jet tool for xmas and not an old spanner)
So ill drop a 22o in and work back from there, thats saved about 3 hours of screwing with jets at the track.
So how come the piston ports dont use the same volume of charge ? i thought the reeds would have been more economical ? spo to speak what am i missing here that its about time i learnt about, ( my first piston port)
-
Ok the cut away was on 3 and it still wouldnt come on the top end but when i put a 1.5 it went off its face, but then struggled in the bottom end ( also stalled on deceleration) can someone therefore post what the standard carb settings for the 74/75 TM 250 are please :
Main Jet =180-190
Pilot = 35
Cut away = book says 3. ?
Needle = 6Dp17
These piston ports seem to be tempermental balance, so i think stock is on the cards to get this new bike sorted and then ill work from there. Plug was a good colour, just ran like a pig depending on the cut away and it swung both was dramatically from top to bottom.
cheers . we are getting closer !
-
This is straight out of the owners manual TM250L
main jet 210
jet needle 6DP1-2nd
needle jet 0-6
cut-away 1.5
pilot jet 35
pilot air adjusting screw 1 and a half turns back open
float level 25 mm
-
Parts catallogue
lists pilot jet at # 40
jet options #230-210-220-240-250-260-270
The rest is the same as Halo1963 post
-
i am giving up on parts books and manuals they all seem to say somthing differant. i was trying to get it stock so i can get it right from there, but stock seems to be many variations:
my testing so far seems to point to this thing only running like it should on a 200 main, ( 210 flat track) <35 pilot and a <2.5 cut away, any other combo seems to either bog down on the main or bog down on the bottom i just cant seem to get the balance it seems to go left or right and not balance out, im going to get a new inlet rubber incase some air is leaning it out at the wrong times.
-
Got the same thing happening with mine , seems to load up as if it's flooding .
Checked float level all good there -main jet is 200 with a 35 pilot ???
Freaky did you manage to sort yours out ????
-
Yep. I think the problem is the piston port set up, under throttle the charge is too rich and cant spark it when its open wide and loaded up on short tracks it kills itself in a cyclical manner. In the end i found the 180 Jet and a 25 pilot fixed the problem but thats only on the short track i ran it on the long track with a 190 and it was ok too, seems the cycle of flooding bogs it dwon and kills off the combustion, charge and its all down hill from there till you throttle off, it clears out and then you force it again with a poor mix. I only got a TM this year and now 3 bikes later it seems they all suffer from the same problem, i have no idea how the piston port works but with out the reeds it seems a balanceing act to set it up right, err on the lean and its fine. the sympton was very muck like it was running out of petrol which was what confused me all the time, and you could rev it standing no probs at all, it was only when ridden did the problem show itself.
Im not sure of the track you on but if it has small straight and 3/4 throttle cut the pilot down to 25 and then jet your main around the 180-190 from plug chops. test that and if it runs off its face then you now your onto it, but do short runs so you dont run it too lean until you get your mains right, you might find with a 25-30 pilot you can support up to the 200 main, its just getting the transition right but dropping the pilot and main will tell you instantly if your heading in the right direction or its another issue.
Why ? well I found runniing lean on the pilot got it into a good balance so when the main came on it was still n the pipe and not hit with a charge it couldnt handle.
I firmly believe the 74/75 TM250 Should be on A 180 Jet unless you on 100mtr plus flat out straights then you can use the 190-200 sparingly
I got all 3 bikes as they are and told they ran, they did but not propally for racing my tracks, they all bogged down, so im guessing they where jetted over the years for trail riding and the kids etc. and maybe just there is some change in the older Super fuels to new unleaded in these piston ports ,that has a knock on effect in perforance/fuel characteristics for combustion as a full charge hit.
Im not sure though if you have always had the bike why something has changed now if thats the case im not sure this is your problem , but if its a new purchase or an old problem for you i would put my money on you pilot and main being too rich and maybe an averge spark from either the plug ( change it) and maybe a coil or winding thats getting a little weak or tired.
-
Thanks for the reply , Freaky I test ride my machines at home ;D as I live on acreage
This sarvo I went out and bought jets ranging from 180 to 290 in steps of 10
Also bought pilots 15 20 25 30 35 40 plus 4 plugs ;) so it's out to me mates farm ( Flat with a gully - ) which would come close to most of the QLD courses .
I also have a NOS RH 250 barrel that I might drop on and see if there is any performance gains ::) just need to find a manifold intake , as they are 3 bolt
-
Freakster, if it's happening at three-quarter throttle and under load, shouldn't you be leaning off the needle a notch or maybe two ? If your mainjet is in the ballpark, your needle setting is much more critical from quarter to three-quarter throttle really, worth a try before you go nuts with a pocket full of main jets. :o
-
Its me with the pocket full of jets ??? spent the last hour changing jets and needle positions
Just checked the parts book and yes it has the right CDI unit Part # 31900- 30120
The thing that's spinning me out is , it idles like a dream -give it a hand full of throttle and she revs over the moon .Put it in gear and it loads up big time ::)
Might try a different carb ( pe 250 )
-
Its me with the pocket full of jets ??? spent the last hour changing jets and needle positions
Just checked the parts book and yes it has the right CDI unit Part # 31900- 30120
The thing that's spinning me out is , it idles like a dream -give it a hand full of throttle and she revs over the moon .Put it in gear and it loads up big time ::)
Might try a different carb ( pe 250 )
testing a carb you would need the same one, size etc 32mm anything else is futile.
put the 25 and the 180 in the bitch and thats the only test youll need to do to prove this is your problem. you need not read nay further till you have done that. ;) put the 180 in the bike and dont come back to you have. >:(
Mine sounded the same reved on the stand, blah blah blah. put it on the track and it filled up. lean it out on the pilot and then the main as discussed 25/180 and see if it make a differance under load, if it dont make any obvious change you looking in the wrong spot. full stop.
if it cant get on the pipe with those jets i would move onto the stator, coil and cdi, get all 3 tested as a set to see if they work under load, if you cant get an immediate change on the jets you need to suss your electrics, pull off the lot and post it to steve ( betta bikes) or similar even lozza was taking about building a bench tester up. you need to know the spark is working under load, big fuel will kill a little spark dead - its a 2 pronged death.
Step one - do the quick and dirty jet test
step two - get the complete electrics bench raced especial the CDI (warm) they go mental after a while.
step 3 - tighten down you barrel nuts again
step 4 - do leak down test (visually check all gaskets and seals with access to the crank)
step 5 - buy another one and come back to it after 2 month ( that worked for me) i had gotten to close to the problem ans it was staring me in the face. although yours might be differant it sounds related to one of the above, from living the problem first hand :O)
-
Freakster, if it's happening at three-quarter throttle and under load, shouldn't you be leaning off the needle a notch or maybe two ? If your mainjet is in the ballpark, your needle setting is much more critical from quarter to three-quarter throttle really, worth a try before you go nuts with a pocket full of main jets. :o
NAh its a bigger hit than that, the needle wont help much until he has sorted out the jets, its too much of a differance to pick up on a needle. if its the same thing he will wind on the throttle and when its going 1/2 wide open it will die like its out of fuel, hell wind it back and it will clear and bubble along, then he'll turn it on and again it ll motor along then die again like the spark's dead and its got not fuel to keep up, might even be rattling at this point like marbles as the ingnition/ combustions comes and goes.
its going to be flat as a tack, he will go mental and finanly give up after he has pulled the thing apart more time than ever in its life.
If its the same problem i had this is the solution.
what old farty didnt say was how it was before this and whether it has always been able to get on the pipe with those jets, or if it ever did propally on a track and not just his mates farm.
i have another theory and its related to unleaded fuels, im still to be convienced unleaded octane has the same characteristics in early 2 stokes as the super leaded did, and these piston ports from my brief association with them seem to be very fussy about fuel dumps. Without the reeds to atomise and meter the flow on a curve, the open or closed style piston ports seems to me, to now need closer scrutiny on the fuel ratios, oil ratios and the conversion to atomised usable combustion.
I have still got some elf Kart oxigentator here, i hope to test next time out to see if any differance is had by blends in the fuel. I know ill be lampooned by the forum petrol engineers, but these TM motors dont seem to run what i would call well on unleaded and there must be a reason for that, especially if they ran fine on there current carby set ups for the last 10 years on lead based case. Somthing has to have change on them all for this to be a common problem. Where there is smoke................. put out the fire. heheh
anyhow sorry im rambling now. i have no reason to believe anything other than i have no other explaination at this point for all 3 of my TM 250's running flat on the tune that i got them in, its just another theory, or simply the TM is a shit motor compared to the many small frame honda and yamaha reedies i have tuned over the years. i have no real idea im a Suzi noob but the tune they are in now is shit and not what i would consider acceptable power, i would be happy for a doc or lozza ro make them run like they should if there is another answer :'(
-
Freaky
I am the new owner ....picked it up last weekend , No it won't drive me mental as I have plenty of other projects to pass the time away .
I had the same sort of problem with Docs Mighty TS 400 , problem was solved by using me Pe 400 carb with with 55 pilot and 320 mains using high octane racing fuel
Will try the 25 pilot and 180 mains ...if that don't work I'll take your advise and get the electrics checked out
I recon your spot on about the fuels , might drop a litre or two of AV gas in to see if the works :)
Sheezas look at the time ......good night
-
Having trouble working out what the problem might be Freaky, but I think there maybe something very basic like float height to low or something like that.Has the inlet port been modified? The symptoms you describe don't sound like engine sound more like fuel to me.
Hows the foot Stew?
-
i tell ya 180 mains will fix it ! its the shit unleaded....................
-
i tell ya 180 mains will fix it ! its the shit unleaded....................
Try some 100 Octane race fuel with a lead replacement additive and an octane booster mixed in. It works a treat and the leftovers really get the whipper-snipper going too ;D ;D ;D
-
Have you looked at the "Needle Jet 'O-6' ". Is it worn?? In my experience(which could be sh!t all) the needle jet wears oval shaped and half throttle becomes every flat/rich and makes the bike hard to get on the pipe. Also check the needle for any kinks/bends. I understand what you are saying about dropping the pilot (25) and the main(180) and if it runs with those jets great, but is it still short on mid-range, then try a smaller needle jet of 'O-4' or at least a new O-6.
-
I hear you DJR, what im trying to get him to do is make a big impact , big enough so we can say carby(fuel) or not .
he can always fine tune it after we get the biatch going properly.
180 ! 180 ! 180 ! 180 !!!!!!!!
-
So, you're virtually saying, try a 180 jet, then.... :D
-
Todays up date ..... Installed a 25 piolt along with 180 as suggested along with new fuel ( shell optimax ) ....kick kick kick ring ding ding ringgg
ringggggg ding ding put it into gear let the clutch out ring blurp blurp blurr then loads up.
Change the main jet to 170 ..... stationary it revs its tits off same old thing when under load it dies in the arse very much the same as the old CR 125 did when they flooded
Freaky I'm getting good at changing mains and pilots under 4 minutes flat ;D ;D ;D
Sprayed aero start around the intake manifold while motor was running and there was no change in revs which is a good sign
Next I will check out the timming ....might rotate the base plate a little to see what results I get ???
-
Its not the jets.
You have a differant problem.
next change the carby incase you got something funky going on in the guts of it, floats ,fuel shut off needle etc
next take the whole ignition off and send it to someone to test it, specially those black boxes, mine died as soon as i did the jet change, i put in a tm 400 to test it and it went like stink out the garage door. the original black box has never worked since F.N.W
LEave the 180 jet in it and push the pilot back to 35. thats you base. now you can piss about with everything else until somthing make it go rinngga ding ding barrrrrrp baaaarrp :o
Failing all that take it to CD5 and march right up to Joel and say fix this big guy ;D
-
Get out your original and or Clymer type manual and go to the ignition section-I have had several electrical problems over the years that I would have sworn were fuel related.Then get a multi-meter with ohms etc capabilities and start checking readings as per manual.My last one proved to be the last thing I checked-the secondary or plug cap lead coming off the ignition coil was as dead as a maggot-the bike would start easily but under load(higher RPM) and would break up badly,like it was out of fuel or spark etc.I put a 2nd hand coil on I had available and presto- a very long standing problem fixed.Next move was going to be a "leak-down" test to check for any air leaks and if that didn't fix it ,I would gladly have torched it-stick with it and do the simple things first.