Mk1 no idle, serging at low RPM? Please Help!!!!

colin40bikes · Post by **colin40bikes** » 05 Jan 2006, 21:27

Bought this Mk1 from a friend of a friend to get me back into trail riding on the cheap. When I got it it had been stud for a year so the fact it didn't run well at the bottom end didn't bother me. First thing I did was a full check and service (It didn't even have a plug cap, just HT wound around the plug) With this all done new 2sroke, fuel, plug cap etc it still ran exacly the same. L.T. advised that the CR silencer may be the problem. Fitted new DEP for a CRM and still the same. L.T. then advised soaking carb in coke and new pilot jet with a good blow out. All this done and still the same. L.T. then told me to check the inlet and reeds. All ok here. L.T. then recomended a carb overhall kit. Carb off, yet again, more coke and air rebuilt with new kit and yep still the same. L.T. now tell me the only thing left is to replace the left side crank seal. This I have just done but the dam thing is still the same. I do not have a clue what to try now! PLEASE HELP

CRMR · Post by **CRMR** » 05 Jan 2006, 22:19

Hi mate , sorry to here your having problems with your crm ,, Have you searched the forums ,, There are endless posts about the problem your having and endless replies ,, My first sugestion is to forget leisure trail for the moment and methodically go through all your options,, Its seems from what little info you have given us you have covered all the right bases ,,But dont forget , just because you serviced the carb it seems to be working ok , there may still be a problem ..So first of all , tell us exactily whats wrong , If it works fine at high revs but shite at low revs then it still may be a carb problem , Have you checked your powervalve settings,,Have you looked up you exhaust port to see if your piston is showing sighns of blowback (busted rings)??????As for soaking the carb in coke ,,Hmmm , cokes better up you nose mate than as a carb cleaner..How far have you actually stripped the carb ,, it all sounds like a blocked jet to me ,,

colin40bikes · Post by **colin40bikes** » 06 Jan 2006, 10:55

I work at a race engine build shop and have the use of an ultrasound cleaner with which I cleaned the carb b4 the coke bath. I have checked power valve setting as best I can but as the thing will not idle its not that easy, but I think its ok. I also do not think its something major like the engine because it runs great mid to top rpm.
It seems like a blocked jet or an air leak to me but I think I have covered all bases here.
As for L.T. they have been a great help but without taking the bike to them, and paying money I don't have, They seem as stumped as me!

WHAT NEXT??? PLEASE HELP!!!!

CRMR · Post by **CRMR** » 06 Jan 2006, 18:45

Timing may be out? I know its preset and virtually unadjustable but if you have a worn collet in the flywheel this could throught it out a tad ,Also , Sparkplug gap has to be spot on for lower rpm handling,Have you bought a plug cap with an internal resistor and also an (r) rated plug aswell ,ie BR8ES...The r stands for resister too , You dont want two lots of resistance..Have you done a compression test yet??...How do you know the powervalves working ,Have you looked up the exhaust port yet..Is your piston clean , Is the powervale returning home on idle ??With the engine running the powervalve motor will move on its own and look like its working because of the exhaust gasses passing by it..Tug at the two cables ,, see if there broke,One mignt no be returning properly....

Like you im puling at straws too but you never know , you might get lucky with a quick fix

colin40bikes · Post by **colin40bikes** » 07 Jan 2006, 17:54

Just come in after spending another 2 hours on the beast! Everything on the flywheel and crank looks good so I don't think the timing is out but I have not checked with a timing light. Plug gap is spot on and is a new B8EGV. The plug cap is a new NGK which I think is a resistor type my local bike shop sold it me as the one for the job. Removed the exhaust and looked up the exhaust port all looks very good, nice bore & piston, no busted rings so I did a compession test with that being all ok aswell-THANK GOD! I then removed the power valve cables, both are free in good condition. The power valve moves ok and is not sticking. Back together again ( it always takes several kicks to fire up ). I left the power valve cover off it seems to open and close ok but, as I say, it will not idle so setting it is difficult. With it running if I hold the throttle perfecly still and open enough to keep it running it serges up and down untill eventually it dies. I have got the mixture screw 2 1/4 turns out turning it in or out 1/2 a turn makes little or no difference.

HELP!!!!

Anybody interested in buying it as it is?

colin40bikes · Post by **colin40bikes** » 07 Jan 2006, 17:54

Just come in after spending another 2 hours on the beast! Everything on the flywheel and crank looks good so I don't think the timing is out but I have not checked with a timing light. Plug gap is spot on and is a new B8EGV. The plug cap is a new NGK which I think is a resistor type my local bike shop sold it me as the one for the job. Removed the exhaust and looked up the exhaust port all looks very good, nice bore & piston, no busted rings so I did a compession test with that being all ok aswell-THANK GOD! I then removed the power valve cables, both are free in good condition. The power valve moves ok and is not sticking. Back together again ( it always takes several kicks to fire up ). I left the power valve cover off it seems to open and close ok but, as I say, it will not idle so setting it is difficult. With it running if I hold the throttle perfecly still and open enough to keep it running it serges up and down untill eventually it dies. I have got the mixture screw 2 1/4 turns out turning it in or out 1/2 a turn makes little or no difference.

HELP!!!!

Anybody interested in buying it as it is?

mmaatt25 · Post by **mmaatt25** » 08 Jan 2006, 01:07

HI,

Seems like you've checked all the obvious things, one quick thing to check is for air leaks around the carb/inlet manifold.
If you spray brake cleaner or easy start around this area when the engines running it will start to revving if you've an airleak.
Spare air drawn in causes the engine to run lean, so at higher revs it will fly.

Matt

kinney · Post by **kinney** » 08 Jan 2006, 02:23

Hi Col,
It really does still sound like carb trouble. Have you stripped the carb and set everything as per manual. Have you got a CRM manual?
Check the exploded view to see if there is anything missing. This isn't as daft as it sounds!
Is the float height deffinately correct. Where are you measuring it and what have you set it to?
Which groove is the clip in, on the main needle?
Have you stripped every single jet out and blown them and the galleries through?
It the choke plunger sealing OK?
Is there excessive smoke coming from the exhaust when you're keeping it running at low rpm.
Double check that all parts are present inside the carb with the manual.
Try another batch of petrol....you never know.
Just trying to get a feel for this problem, let me know about the points above.
Hopefully we'll sort this soon.
Andy.

colin40bikes · Post by **colin40bikes** » 08 Jan 2006, 22:15

Hi Gents, thanks for your help so far

The manual I have is the L.T. one off the internet I can tell of nothing missing but I will check again when I get some time. L.T. did the float height for me and as it doesn't flood and runs great at high rpm it must be O.K. ? ( also fitted all new breather pipes ). I've got the needle on the middle clip as per manual. I've stipped the carb COMPLETLY. Blown out all jets etc given it all a good ultrasound clean twice. Then on L.T's advice I gave it a coke bath and blow out with a new 45 pilot jet. There is no excessive smoke and I have changed the petrol and two stroke oil at least twice. I do know quite a bit about engines etc but have no experience with crms. Its just got to be a carb or air leake problem? Last time I ran it I sprayed wd40 all over the inlet and inside the flywheel ( to check crank seal ) but still no change.
This problem makes me want to pull my hair out all I ever here about CRMs is how great and reliable they are.

I will take the carb off again next and double check with the manual or if I can get some cash together let L.T. have it to check.
Thanks again, Colin.

CRMR · Post by **CRMR** » 10 Jan 2006, 17:09

have you checked your REEDS and what condition are they and the gaskets in ,Sounds to me that under low pressure you have an air intake leak but under pressure(high revs) the leak closes up ,Imagine a flap that sucks itself closed at hi pressure?

. dunno ,, straw clutching again ,

colin40bikes · Post by **colin40bikes** » 10 Jan 2006, 21:13

Hi, Thanks again for the help

I've removed the reed block checked the reeds and put the manifold section on a vacuum tester ( bocked off oil inlet hole ) all ok.
I've got the carb off again at the moment. I've double checked with the manual all seems correct. I've put the thing in the ultrasound cleaner again and checked every single hole and passage it all seems perfect. All at a loss as to what to try next

Please help! Should I take it to L.T? What do you think it will cost?
Thanks, Colin

Bargos · Post by **Bargos** » 15 Jan 2006, 12:27

Colin,

Is it worth trying another carb, just be sure? My mate has a working spare for a Mark1 and he only wants 15 or 20 quid for it. At least that way you will know for sure and it has to be cheaper than LT.

At least this way you can be certain of whether that is part of the problem and we could then help you to look at other areas.

Where are you based?

B.

colin40bikes · Post by **colin40bikes** » 15 Jan 2006, 12:54

Hi Bargos,
Fitting a carb that works sounds like a great plan. Is your mate's comlplete with slide needle etc?.
I have just put the bike back together again but I can't try it as I have left the exhaust at work, I am getting old!
I live close to Derby but if you email me your contact details [email protected] we can work something out.
Thanks for your help,
Colin