HI I have recently purchased a mk2, having done cosmetic work I decided to give the bike a spin, however I discovered a misfire when on full throttle , I an reasonably technically minded but this has got me stumped, the bike runs fine on tick over and when reved moderately, but when reved hard it misfires and spits back thorugh the carb, I have checked all the obvious things and have fitted a new plug (B8EG),there is no leak in the inlet, all the mixtures are OK, could it be crank seals?, or a blocked air duct in the carb?

Has any one had any similar problems or have any answers I would be very gratefull, Cheers

(I'm probably confusing misfire with backfire, but what the hey... )

I assume that you have previously removed the tank? if so, check that the the breather/vacuum hoses are connected properly...

Hi TiN, MY BIKES GOT A CR250 TANK FITTED, THE ONLY PIPES CONNECTED TO THE TANK IS THE FUEL LINE AND A PIPE THAT COMES OF THE FILLER CAP, IS THERE SOMETHING MISSING ON MY BIKE?

Erm, you're probably far more technically-minded than me...but after a quick bit o' Googling, I found something about mis-firing at high revs, and it can be caused by a dodgy secondary coil (whatever that is - by the spark plug apparently )...the coil will eventually fail completely and thus prevent the engine from even starting...this was for a pre-97 CR250 though and not specifically for CRMs.

I've only been a CRM owner for 3 days ...and the bike is currently stored at a friend's house!

Sorry for not being of much help...

THANKS TiN, Ill have a look, although I checked the coil by swapping the coil off my KX125, and the CRM still misfires!!!, see what I mean about frustrating !??? I hope you are enjoying your new CRM.

Good luck in tracking down the problem. I have said it before and will say it again, clean the earths and kill switch (and i would have gotten away with it, if it wasn't for that pesky kill switch). Seriously they can do some wierd poo to the bikes running. I thought i had lost a ring for about 10 miles 2 up. yep still kept riding it as i needed to get back, to find after a flick of the switch it suddenly wanted to tickover and behave normally.

Thanks Admin, Ill try that as well, Christ Im going to be busy, Ill let you know how I get on, I may need some more help in the future. Ill ring LeisureTrail today and get them to send me a manual as I can not find the link on the site,

Regards, R Collins.

Er, have you checked you mail

R Collins (!)

It sounds like an electrical fault to me and it will definitely be worth checking that your HT lead and plug cap arent shorting out anywhere and are secure. Plug caps can break down a bit and cause misfires. Where are you based?

Christ Lads, cant keep up with all the mail!!!!!!!, thanks Paul got mail, thanks Bargos, Ill try to locate a new coil, as I dont think the HT lead you can replace can you?

Kind Regards R Collins.

PS, Based in Peterborough, Cambs.

on my old crossers i used to make my own ht leads, just pull or unscrew your one out of your coil and get the ht lead from a car and screw it into your own coil, then if you want you can put your own cap on it but i just used to leave the car one on it, worked just as good. i have never bothered to look at mine because it runs fine

see, told you that i didn't know nuffin'!

on the subject of HT leads though - is that the only route to installing a tacho onto a CRM? I wanted one of them tarty Revlight things, but they need an existing tacho to read from

Cheers (and sorry for the hijack)

ur talking about legal road requirements aint ya? sorry cant help u out there! rev counter whats one of them for?

definatley sounds like an electrical fault, not a dreaded knackered cdi is it?
got any pics of the bike with the cr tank on?

Hi, Spent all day messing with CRM, looks like I have sorted the misfire, seems that all of the air passages on the carb were blocked, therefore when on full revs, pressure was building up in the carb and the only way for it to escape was back through the carb, causing the spitting back hence the misfire!!!!!!, are you still with me??!!. got carb soaking in good old coco cola bloody good stuff, imagine what it does to your gut !!!!!, Ill let you all know if this does the trick, Yes I have got pictures of the bike when I brought it, and will be taking some once I get it back together tonight/tomorrow,Ill then post them on the site, the once I have finished I had better get some work done!!, these CRMs are more addictive than my Ducati 748!!!!!!!!!
regards, R