2 Stroke engine problem, need help please

[D6]

Muddy water scoured the carb slide & body you're leaking air through your carb top work. Carb gets hotter, gap gets bigger, more air finds it's way in, bypassing jets.

seen a lot of carbs scoured badly but work ok, worth a try though, is there a seal on the carb top?
ps, blowing through your carb with compressed air isnt a good idea,you can lodge debris in the carb drillings, the jets look clear but the actual carb could be (partially) blocked

 

[millard]

My thought is you've got an air leak at the carb top.

Back when I used to spanner for a living we'd spray something all around the carb and manifold to locate an airleak on a running engine, but I can't remember what.
WD40? Carb cleaner? Brake cleaner?
Been a long time...

I'll try Easy-Start on it today, cheers BM

 

[millard]

seen a lot of carbs scoured badly but work ok, worth a try though, is there a seal on the carb top?
ps, blowing through your carb with compressed air isnt a good idea,you can lodge debris in the carb drillings, the jets look clear but the actual carb could be (partially) blocked

Digg
yeah there is a seal in the top, I'll check it.
When I blow air through I can feel it exiting the other end of the drillings.

 

[(RIP) Kaister]

slacken or remove the throttle cable

turn your idle mixture in to stop then out 1 turn

back your idle stop screw right out till you can't feel the slide touching it.

now what happens ?

i think it'll be your carbslides worn and leaking air past when shut tho'.

had a guzzi lm did the exact same thing - thats what 40k miles on open bellmouths does tho.

 

[millard]

To see if the revs would increase by finding the air leak I sprayed some Easy-Start all around the carb, reed block and inlet stub, no difference. I removed the air filter and spayed it directly down the carb but killed it the first time. Second time I sprayed a bit less and the revs calmed down a bit. I'm assuming that what happened here is that the mixture was enriched temporarily by the ether in the spray, so for a short while getting rid of the weak mixture. Dunno if it helps though, still haven't found the scource of the leak, if there is one. Pinning all my hopes on an increase in pilot jet size now as suggested by a coupla guys on the CRM250 forum.

 

[D6]

so you went through water and now u need a bigger pilot jet??the jet didnt shrink in the water,
it points to a partially blocked carb drillin if it helps, if the carb then clears ul be runnin rich then

 

[millard]

so you went through water and now u need a bigger pilot jet??the jet didnt shrink in the water,
it points to a partially blocked carb drillin if it helps, if the carb then clears ul be runnin rich then

yeah I know mate, it's just that a coupla the guys on the CRM forum are very insistant that I try it, so for a few quids worth of new jet i'll try. But as you say, I reckon it might just mask the problem. Don't know what else to try apart from a carb but can't raise a loaner yet.

 

[D6]

well its worth a try as you say , you can always change it back if it clears

 

[millard]

so you went through water and now u need a bigger pilot jet??the jet didnt shrink in the water,
it points to a partially blocked carb drillin if it helps, if the carb then clears ul be runnin rich then

Just to clarify, it wasn't just a soaking in water, it was a very muddy puddle, this was the result

it wouldn't start untill I removed and cleaned the mud off the spark plug electrodes. I know I should have van'd it home but was out in the middle of the Plain so didn't have a lot of choice really. That's when the symptoms started to show, on the ride back to the van, steadily became more noticeable.
In one way i'm glad because on investigation the big end and mains were shot and woulda given way sometime soon.

here's the big end bearing

thanks for all your suggestions so far.
millard

 

[Deleted account 211025001]

so you went through water and now u need a bigger pilot jet??the jet didnt shrink in the water,
it points to a partially blocked carb drillin if it helps, if the carb then clears ul be runnin rich then

Gotta say it sounds like that to me too.

Went through similar with my TDR (except it was like that when bought, not due to muddy puddles ).

After the third complete carb strip down, clean, float height set it all suddenly worked ok Given the piccies you showed my money is on still having some shite in the carb

Good luck though, sounds like a right 'mare

Andres

 

[alimey4u2]

Carb cleaning services...

www.bestultrasonic.com

 

[vilguy]

Ive had 5 crm250s, presently got enough bits to build 2 in the garage. If you want anything give me a shout. Im clearing it all out cheap now as i need the space.

Mine was doing something quite similar and it was something simple - the clamp strap that tightened the airbox around the carb had snapped and air was leaking in. Replaced and hey presto. Back to perfect running low down.

The crms a tough little cookie and can take immense abuse without problems.

Like i said though, gimme a shout if you do want to swap anything. I had a spare carb if it does turn out to be a heavily worn carb (doubt it). Definetely wants a good clean out though. I just chuck my carbs in a bowl of fresh petrol and use a brush on it, whip the jets out, blow through them in your mouth. JD

Other things to check though, powervalve operating correctly? Not got it adjusted wrong have you? is it functioning?

Paul

 

[motoscot]

still sounds like a crank seal leaking

Steve onyack

 

[vilguy]

Could be, were these replaced during the rebuild? - sorry just re read your initial post where you stated you had.

It would be the very last thing i would check though.. for the obvious reason that its frickin expensive and annoying stripping it down again.

2 strokes only ever go wrong in 2 ways - BIG TIME or something really simple yet annoying haha

Other thing is...crms are fickle little buggers sometime. My last mk3 was rebuilt with top bits, but did something similar to what you describe. Could never stop it as it seemed to just be what the engine wanted to do. I turned the idle screw right out so it was just pop... pop..... pop...but wouldnt idle when cold without the choke (not left that on have you! Mine used to rev its tits off if the choke was left on more than 30 seconds)

once warm though it would just sit there ticking over lovely.

As a starter though, put all the jetting back to standard (unless you have a full dep on it). Make sure the air filter is oiled (otherwise itll run lean)

Take it out for a spin and do a plug chop. Thats the simplest way of seeing how its running.

Paul

 

[Shep]

still sounds like a crank seal leaking

Steve onyack

That's what I was thinking, all that shite in the engine has scored the smooth sealing area on the crank

Shep

 

[millard]

Carb cleaning services...

www.bestultrasonic.com

Cheers alimey
I might just invest in one of those. had a look on ebay and there's some to be had for around £30, dunno if they'd be any good at that price though.

 

[millard]

Could be, were these replaced during the rebuild? - sorry just re read your initial post where you stated you had.

It would be the very last thing i would check though.. for the obvious reason that its frickin expensive and annoying stripping it down again.

2 strokes only ever go wrong in 2 ways - BIG TIME or something really simple yet annoying haha

Other thing is...crms are fickle little buggers sometime. My last mk3 was rebuilt with top bits, but did something similar to what you describe. Could never stop it as it seemed to just be what the engine wanted to do. I turned the idle screw right out so it was just pop... pop..... pop...but wouldnt idle when cold without the choke (not left that on have you! Mine used to rev its tits off if the choke was left on more than 30 seconds)

once warm though it would just sit there ticking over lovely.

As a starter though, put all the jetting back to standard (unless you have a full dep on it). Make sure the air filter is oiled (otherwise itll run lean)

Take it out for a spin and do a plug chop. Thats the simplest way of seeing how its running.

Paul

I'm gonna strip the carb again and this time carefully poke through all the drillings with soft copper wire rather than carb cleaner and airline.
Was thinking on it over the weekend and as I've checked out all the other areas where air could leak in but it's still running weak then I'm coming to the conclusion that rather than an over supply of air it's likely to be an undersupply of go juice.
Probably be wrong again but it's worth a try.

 

[millard]

That's what I was thinking, all that shite in the engine has scored the smooth sealing area on the crank

Shep

Shep
I did a pressure test on the cases and combustion chanber and it's all good, I also filled the cases with petrol up past the level of the crank seals and it was dry as a bone on the outside.

 

[Shep]

Yes, it does look as if you've been very thorough, but the fault does sound like an air leak and the seals could leak only while the crank is rotating, you've checked most other things so far

Good luck anyway, these type of faults are always a pig to find, timings ok I suppose?

Shep

 

[millard]

Yes, it does look as if you've been very thorough, but the fault does sound like an air leak and the seals could leak only while the crank is rotating, you've checked most other things so far

Good luck anyway, these type of faults are always a pig to find, timings ok I suppose?

Shep

no adjustment on the timing, it's right or it's fukked.