Guys,

Riding home fairly rapid on road tonight and the bike started acting like it was running out of petrol, you know the thing, it revved fine on part throttle but if you wound it back to full throttle then it just bogged down?

Went onto reserve thinking that would solve it but no, it still bogged down and sounded like it was misfiring a little on overrunvery odd and not in a good way...praying it ain't the CDI or anything similar....Any thoughts?

Hopefully in the light of day I might know more.....

Anyone got any guesses? Plug perhaps? Carb?

HELP?

did it go suddenly or gradually build up to it?

It's been running fine, just happened?

I'm thinking a carb strip and clean the jets? Any suggestions?

All help or suggestions gratefully received!!

that sounds like a good start (that and the plug), check yer reed valves, then check yer 2 stroke oil level too, tyre pressures etc, and then when you've finished clutching at straws (but it's probably best to check everything before) CDI etc

how many km's has it done? was it blowing smoke out the back?

Didn't notice any more smoke out the back than usual

It's done 10k km.

Now I'm no rocket scientist and I hate fiddling with carbs but from the below:
http://auto.howstuffworks.com/framed.ht ... rb101.html

My very general guess is the main jet at the moment, as the problem seems to be from 1/2 to full throttle?

At the same time I'll clean the air filter, actually is it worth buying one of those filter cleaning kits by Silkolene or similar, or is there a just as good cheapskate way of doing it?

backfiring usually indicates a lean mixture...(realise that it's doing it now I'v re read your top post )

I'd take the pipe off the carb and make sure that petrol comes out in a nice steady flow

then i'd take the carb off and make sure it's not all blocked (check idle and main first)

send me your email address and I'll send you a drawing of a crm250 carb.....

SUCCESS!!!!


Took out the main jet and the pilot jet, pilot jet was pretty gummed up and the main jet had a mini net over the end!! A nice little wad of fluffy crud stuck in there!!

Blew them both out and emptied the small amount of sediment in the bowl too......

While I was there I thought it wise to check the air filter as the cack had to get in there somehow and bingo, there was the reason I reckon....the air filter has basically started to fall apart, started to come away from the rim part!! New air filter required for me!

Has anyone used the pattern ones for about £8 rather than the Honda job for about £25 from LT? Is it worth shelling out for the Honda one?

I got a honda one, it cam preoiled etc, will be using a patter one next time though!

than manual is http://www.nealfamily.co.uk/crmmanual.tif , it bounced from your Yahoo address to

Now the bike runs well but on the main jet, above the tin baffle thing, on the emulsion tube I think it's called there was a sort of lock nut?

When I undid the jet, it actually unscrewed the whole lot and so I had the emulsion tube out and everything with it which was fine, but when I put it back the locking nut above the baffle was loose so I simply wound it down tight to the baffle and screwed the whole lot back in.
Probably sounds confusing but have a look at the exploded diagram that is on that manual, you'll probably see what I mean?

This lock nut I'm guessing is there to enable you to raise and lower the jet/ emulsion tube slightly so perhaps it sits better with the needle, again I'm guessing.

My fear is that with this wound down tight it could be robbing me of some power at top end as the jet is not as wide open as it possibly could be on full throttle? Waddya think?

Also noticed that the exploded diagram has the pilot jet in the wrong place?? On my bike it was 'engine' side of the main jet whereas on the diagram it seems to show it 'air filter' side?? Anyone else noticed this?

Beanie,

Just put the thing back together - it will only go back together one way!

What makes you think you are being robbed of top end power?

B.

Beanie,

Take off your tank and clean it out - you'll be surprised how much crud is in there.

Make sure you put a small fuel filter between the tank and carb as this will catch the tiny particles the tank filter lets through. They cost about a quid and should stop your carb getting blocked in the future.

Roger.

Beanie,

Take off your tank and clean it out - you'll be surprised how much crud is in there.

Make sure you put a small fuel filter between the tank and carb as this will catch the tiny particles the tank filter lets through. They cost about a quid and should stop your carb getting blocked in the future.

Roger.

Hi Roger,

Hmm...it makes sense when you think about it. We tend to be so concerned and careful about air filters and yet the fuel side of things tends to get ignored?

I wonder how many people (me included) blame a crap air filter for crud in the carb when it's actually casued by the fuel side of things?

I'll get one of those inline filters from M&P and stick that on.

Thanks for the advice mate!

Also, does anyone know what I mean about the small nut above the baffle on the main jet emulsion tube?
Just wondering about power loss as my Mk.2 doesn't tend to wheelie without a LOT of effort? I think it's on standard gearing as it tops out at about 90mph. although it still has the standard exhaust? Don't get me wrong, it's not slow but you read here that it should lift the front easily in second?

Cheers,

Beanie