Help! I killed my CRM250 on its first outing!

[Mutley]

Hi guys, I'm back on (or should that be off?) the road!

Got the piston that Knackered Mk1 pointed out on eBay (thanks for the steer) which took just a few days to arrive from Greece, and HertsMX did the rest. An enginering 'anal' (their words ) mate of theirs re-built that bust water elbow that fell out of the head and did a pretty good job of it by the look of things. I probably would have trailered it back the 100 miles to my place in Hants., but 'er outdoors had the Landy, so obviously I couldn't wait when they said it was done and rode it home. Given it's track record in my hands it was a bit nerve-racking at first, but ended up having a great ride following my nose across country - it seems to go like the clappers - even running in. . .

Bit dismayed though when it wouldn't start this morning. So stripped the carb and checked and cleaned jets etc. Not sure whether that did anything, but it does start every time first kick now

One thing puzzles me and someone may have an idea. idle is a bit slow, but idle screw seems to make no difference at all to tickover rate. The lever the screw bears on doesn't really seem to move. I would have cheked it out when I had the carb on the bench if I knew then, but not sure I want to get it off again. Fortunately the tickover is just about OK, but anyone have experience of the carb tickover adjustment mechanism?

[helisupp]

The tickover knurled screw adjusts the idle on the lever which is controlled by the vacuum bellows on top of the carb, it adjusts the bottom stop of the lever.

The lever should be very free to rotate by finger, as the very slight vacuum in the bellows is controlling the idle, controlled by one of the solenoids. I have a total of 7 carbs, all of them have levers that rotate freely.

Pic attached to show the solenoid (3) that controls the idle speed.



If you pull the hose off the top of the carb and connect a spare piece of hose, suck on the pipe and see what happens, if nothing happens its a carb strip and clean.

But try a good dose of release fluid first (plusgas), then contact cleaner, then WD40.

[Mutley]

Thanks Hellisup. I don't think the lever wants to move, so looks like the carbs coming off again. . .

[Mutley]

While I'm at it (2nd carb strip). . . I hope I might be able to cure something else and I'd be interested if anyone has had this issue too.

The bike has good low-down power but a mid-engine speed, mid-high load mis-fire. It has so much top-end that at first I wasn't put off by this, but the more I ride it the more I realise that more often than not both off and on-road I'm riding in this mis-fire range. The engine stutters, clears it's throat and then takes off like a banshee. It feels like a carb issue (but maybe that's just wishful thinking that it's not something to do with the bike's Apollo 13-like electrics).

The bike has a lot of Mugen stickers on it and the Pwervalve looks like a Mugen casting, but I'm not sure what else- if anything is Mugen. The exhaust is actually an RSV. The last owner clearly changed the jets as the old ones came with the bike and appear to be 148/48 (from memory) for main and pilot respectively (as are the new ones in the bike).

I intend to give the carb a strip, good clean, and check needle position, float height etc. as far as I am able, but would welcome any further tips from anyone who might have experienced a similar mid-range misfire from an otherwise very healthy motor.

[helisupp]

Trying another carb might help, how close are you to Gloucester, I have a couple on the shelf.

Sorry but no loaning of parts, only on site for fault diagnosis.

[Mutley]

Hi helisupp, couple of carbs on the shelf sounds like a good way to go. I'm on Hants/Surrey border so bit of a trek. But thanks for the offer - I'll see how I get on - might take you up.