Hiya everyone. sorry to jump straight onto the forum with a problem but i expect you're used to it. i moved back to a honda after 3 awful years of trying to ride a fuel injected guzzi that broke down every week. in the past 2 years the SH (firestorm here in the UK) has been brilliant , i forgot what it was like to just get on , turn the key and go. but finally the gremlins are back. so here we go.
last week i fitted new stubby straight through cans (this may not be relevant) , the bike ran fine for a week. then a few days ago whilst out riding quite hard the bike missed a bit when rolling on the throttle. the problem slowly got worse. so what happens is the bike starts fine, ticksover , feels normal at low revs but under load , accelerating etc it bogs down, if i hold the throttle wide open it wont accelerate , if i tease the throttle slowly its better , if i run with choke out its better , going downhill its better. it doesnt seem to misfire , just bog down, i cant be sure but i think its both cylinders. sucking on the petcock vacuum i can hold a vacuum , fuel flows from both feeds equally as far as i can tell . with the tank off if i apply a vacuum to get fuel flowing then release it takes a couple of seconds to shut off. the airbox isnt blocked. im running out ideas - please help !

 

A couple basic questions-

Have you inspected the plugs for signs of excessive rich or lean conditions? I would.
When was the last time the carbs were cleaned? Maybe try a little fuel system cleaner at a couple successive refuelings to see if any improvement.

 

sorry i should have said , i changed both plugs and it made no difference , i also tried disconnecting the throttle position sensor and that made no difference. i know i should be getting the carbs off for a clean and check but ive never done it before (on this bike) and as this is my only transport and i live in a very rural area im a bit worried about making things worse , at the moment the bike is rideable.

 

sorry , missed your point. the plugs that came out were different , one paler than the other but both looked fine.

 

if you had the tank off, make sure the vacuum line is on the correct nipple.it should be on the back of the petcock ,not the bottom.

 

ive been reading loads about the petcock so dont worry , that pipes going back on the correct nipple ! just got airbox off , carbs next. but i noticed a small difference in the 'feel' of the slides. the front one doesnt feel particularly smooth compared to the rear one. also there was a trace of clean looking oil on the face of the entry. i did top it up last week so maybe just a bit of extra ?

 

carbs off . kehien 175 mains and 48s pilots

 

178 main in the rear + in getting excited , found a green bogey in the main jet ! its gotta be the cause. surely.

 

Are you in the U.S? Sounds like someone has tuned the carbs already. Also, on your slides, do they return at the same speed after you pull them back?

 

Its fixed ! Im in the sunny UK , a scorching 80' here , just perfect for lovely ride out. So thats all it was , a small green bit of algae sitting on top of a main jet. So a quick note to anyone who's stumbled across this thread because theyve got a similar problem. Dont worry about taking the carbs off and getting in there , i hesitated for a couple of days because i was nervous of getting that involved but it really is quite easy , 1 hour to get off , check and refit. No special tools or skills needed , do check for a quick guide on here though.
Other news . One of the carb rubbers wasnt done up . The bike now runs better than ever , smoother and stronger , rolling on the throttle in first from tickover lifts the front. Im not sure what the standard jetting is but i expect ill find out when i search here.
A big thanks to everyone for their help and i hope this thread may help someone else in the future.
james

 

In the U.S., only 45 pilots were used. If memory serves me correctly, Firestorms sometimes got 48's depending on the year (or something).

 

Ah! Green booger syndrome... Glad it is snot slowing you down anymore.

 

Good job bigpants!

 

GBS.... Similar in symptoms to PVLIR.

James