Engine problems

[atherts01]

I really hope I can get some ideas from everyone here I have a big race on the 15th and my engine is not running like it should. I hillclimb a 1978 gs1000 it is a bone stock motor with stock carbs with dyna coils with dyna jet kit in it unit filters and straight pipes. On the flat ground it will idle and rev up just fine. NO popping or dead spots nothing but when I take off (on the flat) then I start up the hill for first 35- 40 feet on the hill after a jump it bogs down to point that the engine almost dies.Pulled the carbs off and sprayed them out. I checked the floats and they looked were good. Is it fuel and electrical?

[almarconi]

I don't know anything about hill climbing, but I'll bet your engine is starved for fuel. Street bikes are not designed to go over jumps..etc. You probably need some type of a pressurized fuel supply so that fuel is supplied to the carbs no matter what their inclination or attitude. I remember seeing a gs750 setup for hill climbing. You would really need to speak with someone who has setup these type of engines for hill climbing.

Here is the video of the bike

http://www.youtube.com/watch?v=tR5Aev3n7D4

[atherts01]

No I am just running the stock carbs. I am not running fuel pump. But my plugs came out black with the very tip of the plug black a little white. Does anyone run a fuel pump on their bike?

[Dave8338]

Is the float level set correctly? It sounds carb related to me. One thought is that if the float level is set too high, it may bogging out as a result of being too rich. That would explain the black plugs...

I had a circle track 2300 that left me scratching my head until I figured out that when banking hard, the fuel in the bowl would actually "climb" the side to a point is was spilling out the vent and into (unmetered) the secondaries and flooding out.

I'm trying to visualize the CV's (is that what you're running)

[almarconi]

You should contact someone like Harold Waddell, a 3x NAHA national hill climb champion, and ask him for some advice on setting up your bike. Even if he can't, he probably knows someone who can. His website is

http://www.haroldwaddell.com/

[GSJim69]

Here is a guess. While climbing the hill the carb is obviously at an angle. The float level drops allowing more fuel to come in causing a rich mixture.
I know on piston aircraft that perform acrobatics, special fuel and oil systems are installed to keep liquids properly flowing at all angles.

[Big T]

Okay, you say that on flat ground it will idle and rev up fine

How does it run on flat ground? Can you run it thru a couple of gears without bogging?

Just throwing a jet kit in is no guarantee that your jetting is correct

I don't think you need a fuel pump, you just need the jetting correct

And you need to clean the carbs, not just spray some carb cleaner in it

See In The Garage

[almarconi]

I guess with the right jets and some knobby tires my 750L will be ready for the motocross track ?

[reddirtrider]

You can't use a fuel pump on these carbureted bikes. Rule that one out.

I've rebuilt the carbs on dirt bikes many times and I can't think of any real discrepancies between them and the GS carbs - well, they aren't CV's but I'm not sure if that makes any difference in your problem.

I'd have to go along with trying to get the bike running properly on level gound then you may want to play with float height adjustments. Just a guess.

[twiggy2cents]

some newer dirtbike carbs have collars that look like the ones you put on your pets necks to help keep the gas consistant

[flyingace]

I think the poster needs to clear something up.

Is this a new problem? Has the bike been running up hills strong up until now, or is this the first time this bike has been used for hill climbs?

[Dave8338]

My guess is first time runner with need for a complete carb clean, o-rings for the WHOLE team and a set of intake boots. Bump to jet needles, correct float setting, and valves adjusted.

Just a guess...

[GregT]

IMO Twig is on the right track - if in fact the poster's carbs are actually OK and it is jetted/set up to run right on the flat
I've set up carbs for TQ's and sidecar outfits - both of which suffer fom fuel surge. There are several cures.
One is the collar around the mainjet as seen on dirt bikes - this may be enough to keep sufficient fuel around the jet.
One I've used is to cut a piece of brass tube with an ID to just fit over the main, to a length such that it's trapped against the bottom of the float chamber. If the lower end of the tube is notched to allow fuel in, this holds fuel available to the mainjet through pretty well any jump or turn.
And yes, you can pump feed these carbs - not needed here though IMO
That's a whole new subject.

Greg T