Power drop off on full throttle

[Neosophist]

Pilot jets are the stock size (no 35)

Jets are bigger than stock

115/118 or 110 if it's an original model.

I wouldn't worry about the 120's just yet (can always have it dyno'd to check) but they are not super large over stock.

It sounds like fuel delivery.

Intially I noticed a complete lack of power when revving higher into the RPM band. This appeared at around 7.5k. The engine appeared to completely bog down, and the exhaust started to sound like a two stroke.

Today I took the bike for a ride, and kept part throttle on in a lower gear. It then managed to rev cleanly up to about 10k. As soon as I wound on more throttle, it bogged down once again.

Do you get a misfire / running out of fuel type feeling?

Have you messed with the vaccum pipe? It could be old and split / collapsing in on itself or the new one if changed might not be the right material.

I replaced mine with Aquarium type hose and when warm it was soft as jelly and collapsed in onitself at high rpm shutting off the fuel flow.

Also a split vaccum hose can do the same thing.

Would also inspect the fuel tap while the carbs are off.

[Badgerboy]

Hi,

Yes, it feels like it's missing slightly when full throttle is applied. There is certainly a distinct note to the engine when this happens, I'd say it feels like the limiter when it cuts the front bank, but not as pronounced.

I've emailed Rick for a full set of hoses, they are 23 years old now and likely to be suffering a bit! In regards to the fuel tap, what could be the best way to check it other than the filter? I don't think I'll be able to simulate WOT fuel flow with the vacuum from my mouth!

[Neosophist]

Hi,

Yes, it feels like it's missing slightly when full throttle is applied. There is certainly a distinct note to the engine when this happens, I'd say it feels like the limiter when it cuts the front bank, but not as pronounced.

I've emailed Rick for a full set of hoses, they are 23 years old now and likely to be suffering a bit! In regards to the fuel tap, what could be the best way to check it other than the filter? I don't think I'll be able to simulate WOT fuel flow with the vacuum from my mouth!

Sounds like vaccum hose.. as the fuel shuts off (even partially) it'll cause some of the carbs to run out causing a missifre until you back off.

You can take the 4 screws off the fuel tap (make sure you don't have much fuel in the tank or can tilt it to an angle where it's not going to leak)

If you remove the 4 screws, check the diaphram in the tap to make sure there are no tears or holes in it.

Provding it's all ok you can carefully re-assemble it. :-)

New vaccum hose would be first point of call.. it's cheap too and always worth replacing to save hassle.

[Badgerboy]

Well she's up and running well now.

Other than cleaning the carbs (Which were pretty clean to start with) and swapping the ET's around , I replaced the vacuum hose to the fuel tap, the tank breather, and the fuel pipe.

Pull nicely through all the gears now, and as a side benefit idles even better than before.

Thanks for all the tips chaps.