bogging down at 1/4 throttle

[mtwallet]

hi all, took my h2 for a blast earlier and when its below 4000ish rpm and about 1/4 throttle it sort of boggs down and stumbles but if i crack the throttle open it picks up again and revs right through no problem.ive stripped the carbs and cleaned them thoroughly, set the mixture screws 2/14 turns out and balanced all the carbs with a morgan carbtune and its still the same. the revs also hang slightly at 2000 only for a second or so then drop to about 1500 and idles fine, after reading on here i think the hanging revs is down to sucking air in from somewhere possibly carb to head rubbers so ill check them tomorow, any ideas on the bogging/stumbling?

[RedexRobB]

I would say it might be bogging because of the air leak. Spray some carb cleaner round the carb inlet rubbers and if the revs change then you may well have a leak, also check the clamps are done up tight and the airbox sits properly on the top of the carbs.

[mtwallet]

ive just stripped the carbs again, took the rubber between carbs and head off and they looked fine but i cleaned them and put some gasket sealant between them and the head, set the mixture screws at 2 turns out and refitted carbs. took for a ride for a few miles to get up to temp but its still bogging down at part throttle between 3500-4000 rpm, the revs dont seem to hang any more though so thats cured. ive got a set of new plugs on order ( although the ones in now are fairly new and are all a nice brown color), ill stick them in when they arrive and see how it goes and let you know the results.

[Mori Man]

Is it a standard bike ?

Is it not just a trait of the OEM exhaust system being so restrictive coupled with the airfilter ?

Check your carb's internals are also all original and haven't been tuned for a free flowing system and when bike was sold it was taken off, or vice versa.

[mtwallet]

its a standard bike except for a scorpion race can, all carb internals look standard. i dont think its a trait of the bike, it sort of stumbles and hesitates between 3500- 4000 rpm on part throttle but all i have to do is twist the throttle to say half way and itll sort itself out and rev right through fine

[Tirpitz]

The race can is probably responsible for upsetting the fuelling and introducing a big flat spot. Ideally you need to get it on a dyno to check the A/F.

[Mori Man]

Always love how they call slip-on & bolt-on cans " Race "

Who the hell goes racing with a standrad exhaust system on

Dynojet stage one kit should sort it out - follow the instructions, all the dyno work has been done !

MM!

[mtwallet]

i only call it a race can as oposed to slip on or bolt on because it has not for road use stamped on it. i might give the dynojet kit a go as you say all the dyno work has been done, i have the std can too so might stick that back on first and see how it goes