High revs, popping, etc... ('78 750)

[Anonymous]

Hi,
Today, for the second time, my bike (a '78 GS750) started having an odd problem with what seemed like small backfiring (constantly), while riding.

The weird thing is, today (and the time it happened before, a few days ago, the last time it was ridden), I had been riding it for quite some time before hand with no problem.

The bike will start up, after getting off it for a while, and immediatly start doing these silent little pops, each one taking the revvs higher and higher, above 2000 to about 3. When riding, the ride is not smooth at all, as the bike keeps sort of lurching forward as you ride.

I can ride it, but it is REALLY annoying.

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Possibly unrelated, it is always a pain to get my bike started, and I constantly find myself adjusting the idle screw. I usually wind up starting it with some choke (this is probably a "no no"), even on a day like today (80). Otherwise it simply wont fire up.

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I got the bike about a month ago from a garage where it had sat for the off-season. I cleaned up the carbs, adjusted the timing (to get rid of a nasty backfiring problem), and it seemed to be running fine. Now I don't really know what to do... I love the bike

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also unrelated... does anyone know of a nice gas gauge/float combo I can get for my bike?


Thanks so much... sorry for the long winded post
--sam

[Anonymous]

check for any air intake leaks, how does your plugs look?

[Anonymous]

Just bead-blasted my spark plugs....

what's the best way to check for air leaks?

I know of spraying wd-40 or whatnot around... is that the best way?

thanks
--sam

[Anonymous]

i use a small bottle of propane, carb spray and others can catch fire, dont ask me how i know 8O ...my 750 also pops when reved high so i raised the needles 1 notch which fouled the plugs bad, the plugs are on the white side, but what can i do? it runs great so i aint messin with it.

[Anonymous]

Just a stab in the dark here:

Maybe you should get the carbs synched professionally. I've heard it can be a tricky thing to get them perfect. Maybe it would be worth the $$ to do so.

Hope that helps

Rudi

[Anonymous]

my carbs were never touched, still had unbroken paint marks on the adjustment at the top of the slides

[Anonymous]

How did you go about cleaning the carbs?

Did you dismantle them the whole way down to the jets or did you just clean out the float chambers? Could it be possible that you still have gummed up jets?

Also make sure the carbs are synched (or is it sunk? ).

[first timer]

my guess is a leaky intake boot or boots and old intake o rings. my bike was doing the same and one of my boots was shot. try the propane trick or wd 40 if you want see if your idle changes. spay some wd or propane around each one of the intake boots at low idle and see if the idle changes. if it idles up then you have leak some where around the intake boot or o ring.

ryan