‘79 GS850 will only start with fuel directly shot into the engine

[Guest]

I have a 79 gs850 and I am having trouble getting it to start. Once it starts it runs and rides fine. Petcock is new and gas flows fine through that. There is plenty of gas getting into the carbs which is clearly seen from full bowls. Seems like gas isn’t getting from the carbs into the engine when trying to start. Like I said, bike will run and drive well once it gets started but has real trouble with the initial start. Had the carbs off and replaced the main jets and the air/fuel screws so I know those aren’t clogged. Not sure if it is a spark/compression problem or if I might still have something clogged in my carbs somehow. When i take the air box off and squirt gas (not starter fluid) directly into the carb intake the bike will fire up and run. After it gets running like this it will start and run fine once it is assembled, but then the same problem surfaces the next day when i go to start it.

[TxGSrider]

Sounds like you might want to check your valve lash first. Your symptoms are pretty typical of them being too tight.

Oh, and welcome to the forum!

[noahvanwyk]

I should also add that this problem wasn’t happeneing before recently when I took the carbs off to replace the jets. It would always start fine but run poorly before replacing the jets and now that I have replaced the jets and reinstalled the carbs it starts poorly and runs fine.

[Nessism]

The Newbie Mistakes thread linked in my signature may help. First place to start with any problem is catching up all the basic maintenance. Valve lash for sure, points, air filter, clean tank, clean carbs w/fresh O-rings, etc.

Why did you replace the jets anyway?

[noahvanwyk]

Need to take a look at the valve lash because that’s one of the only things I haven’t checked.

Could this problem be related to the choke passages being clogged?

Thanks for the link to that thread, I will take a look at it.

I replaced the jets becasue I was cleaning the carbs and putting new gaskets on them and checked the jets and one of them was all grimy and clogged. I had rebuild kits any ways so I just replaced all the jets

[tom203]

"Could this problem be related to the choke passages being clogged?"

sure, that's why you need to read the stuff about proper cleaning.

[Steve]

Seems like gas isn’t getting from the carbs into the engine when trying to start.

Two things come to mind in this circumstance.
1. Valve clearances are too tight, especially the intakes. You mention you have not checked them yet, do it soon.
2. Like you say, but being a bit more specific, fuel is not getting from the float bowls into the air stream. You replaced the main jets. they have virtually nothing to do with starting the bike. You replaced the air and fuel screws. They don't flow any fuel. Unless damaged, they don't need to be replaced. Ever.

Need to take a look at the valve lash because that’s one of the only things I haven’t checked.

Please don't put this off. Cold starting is not the only benefit of properly-adjusted valves. Tight clearances (the valves always tighten with use) keep the valves off the seats longer, increasing temperatures. Eventually, clearance disappears and the valve spends virtually NO time on the seat to cool off, causing burnt valves and a very expensive repair.

Could this problem be related to the choke passages being clogged?

It is VERY possible, if you have not stripped and dipped the carbs.

.

[Chuck78]

I have had this problem repeatedly 2 years in a row on my 750 that i deleted the starter and starter gears on & downsized the battery (saved well over 10 lbs, 512lbs dry stock, add twinpot mod dual disc + extra wide rims + 1 & 3 sizes larger tires, total weight savings plan dropped whole bike to 460lbs w/1 gal gas + oil).
in my experiences, it is from the poor quality rotten-corn+gasoline blends that we have now. I clean the choke tube, fuel bowl choke tube orifice, & pilot jet/passages real quickly with carb cleaner spray, put it back together, bike starts first kick, immediately, or days later. Ride it a few times or even once and let it sit any duration, 5 or 7 days... no more first kick starts! Let it sit a few weeks, and it takes 15 kicks to start...
this has been on 2 different sets of fully dipped ultrasonic'd aerosol sprayed fully rebuilt carbs, and on 2 different fully rebuilt engine top ends, and a new OEM petcock, new intake boots and o-rings...
the electric start bikes dont have this problem anywhere near this extent, they always start easier than the kicker-only conversion.
i am fairly certain it is the ethanol crap blend of gas the corn lobbyists and republicans are forcing upon us. If only they did their own research to realize they need to be investing in technology to convert the ethanol plants into butanol manufacturing plants...
butanol has almost the same BTU per gallon as gasoline, and is not highly hygroscopic like this ethanol $#!+ is... ethanol is incredibly hygroscopic, it absorbs water vapor out of the air at an alarming rate, and then it turns to a gooey sludge film... pure crap...
Butanol can be run as a direct gasoline replacement, ethanol gives severely reduced efficiency even when only ran in the E10 blends (10% ethanol 90% gasoline). Butanol also us not hygroscopic like ethanol, isopropyl, etc are...

Ethanol also causes corrosion in our carbs, which can also cause restrictions and a no-start condition.

One other note - i pulled a large paper element type fuel filter out of a GS earlier this year that looked perfectly clean and had very low miles, & on a clean fuel tank, but the ethanol gummed up the fuel filter completely, it barely flowed a dribble of gas...pure crap.

I plan to try a set of VM29 smoothbores on the next hot rod engine build, kicker-only, in hopes that the better aluminum alloy and bigger jets needed for the 920cc top end won't allow this issue to happen anymore.
If that still has issues, I will run a set of Z1R/KZ1000R VM28 carbs with accelerator pumps. Being able to crank the throttle rapidly to give extra squirts of fuel manually would alleviate this issue by side stepping it. It always seems that once the fuel starts flowing, it gets cleared out enough to run and ride fine.