Hi Guys So I have been helping a mate out with his MC22, first time I’ve ever had a play with one of these bikes. The bike ran OK before we started, but he said it wasn’t holding constant idle and was boggy at places in the rev range. Still rideable, but it was troubling him. We decided to attempt a carby clean, and honestly the carbies were pretty spotless. Couple of partially blocked jets but for the most part OK. We didn’t touch the float needles, just the jets and pilot screws. The original settings were: 1 & 4: 2 turns out 2 & 3: 2 ¼ turns out The pilot o-rings were misshapen as you’d expect for a bike of this age but weren’t disintegrated. As we didn’t have replacements we just put them back in the way they were. We decided to see what it would do at stock setting so first we put all the pilots to 2.5 turns out. He rode it home like that but said that apart from running well initially after 5-10 minutes it was getting boggy again and stalled a few times. So it ended up being worse than it was originally. I went around to his place on Saturday arvo and we reset the pilots to 2 turns out. I noticed that it was very hard to start but better through the revs. Especially when the choke was on it was better. I took it up the street and so did he but it ran like a dog really. We even tried to ensure the bike was nice and warm (as Melb is freezing cold) but if anything it didn't make any difference. So we changed the settings and put all the pilots to 2 ¼ turns out. It was really hard to start, boggy and just not behaving well. Idled beautifully though. It was like nothing was consistent. The nice idle was deceptive as any hint on revs and it played up shortly after… so you couldn’t even tell if you’d made an improvement or not the reaction was so unpredictable. I played with the idle setting and had it at 1000 rpm idling nicely but when he took it for a ride it was boggy and ran like a dog again. Could hardly start it the thing, warm or cold, choke on or off made no difference. I checked with another mate who has all his pilots at 1 ¾ turns. Maybe we’re just running too rich, I don’t know? These bikes are a pain to get to the plugs so we didn’t have time to rip it down that far to check, but considering the only thing we changed was the pilot screw settings I didn’t want to change anything else until we had it running good enough to ride. I told him to put it back to what it was when we started which he said he would do and let me know. This is where it is at now, and where I left it. It is a bit smokey when cold and he said the clearances haven’t been looked at in at least 30,000 kms so I suspect that is an area that will need attention. What I don’t get is how hypersensitive the carbies seem to be compared to my FZR – everything we did made it worse really. Maybe we just need to put it back to what it was then do the clearances and see what that does? As I mentioned, I didn’t want to start messing with 10 different things – I just wanted to at least ensure his bike was rideable. He replaced the battery which was necessary but it still is really hard to start and totally unpredictable through the rev range. What do you guys think should be next steps? I'm not familiar enough with these bikes to offer much experience.
With it being boggy i'd be checking that the needle's from the needle and seat's still had soft tip's, and that there's no crud causing them to not seal off when the float rise's , maybe check the float/fuel level's too ?
what year is it ? L and N models 1990-1993 1 3/4 turns out, Later R and RR models 2.5 turns out Valve clearances seem like a good idea https://2fiftycc.com/index.php?threads/honda-cbr250rr-mc22-specifications.2521/
Check fuel tap flows freely. MC22 rely on being gravity feed. Fuel tap needs vacuum to open. Often vacuum hose tap can be perished or leaking. Also diaphram in tap may be torn. How good are the inlet rubbers? Torn inlet rubbers can cause weird issues also?
Yeh I think we have to play a bit more. Setting the pilots to 1 3/4 would be a good start, but I don't think he's ever touched the carbies... at least not for 30,000 kms. Maybe it's just been running that rich for so long...?
Putting my money on valve clearances all being too tight or on the tight side of the spec. If it's not been done in 30,000k's they will need doing for sure.
