1977 Suzuki GS750 issue

[JakeBoucher]

Hey guys, sold my 1990 RM250 I payed $200 for. I put a little work into it but no cash into it. Got $250 out of it so I'm happy. I bought a Running 1977 Suzuki GS750 for $300. I fired the bike up and just reved it in neutral for about 5 minutes. It will not idle at all and seems to run odd. It's a 4 cylinder, and I felt the right 2 exhaust pipes and they were warm but not hot. The left 2 pipes were skin burning hot. The bike has 4 carbs 1 for each cylinder. I'm just curious why there is such a temperature difference? Should I clean the carbs and see how it does? It's an air cooled bike and I'm just wondering if the burning hot pipes are normal or the hardly warm pipes are normal? I know this is a dirt bike forum, but whatever

 

[2strokesteve89]

Sounds like 2cylinders running lean (the hot ones) and the other two either rich or misfiring. You can identify a misfiring cylinder by disabling 1 cylinder at a time, pulling a plug wire, or if they are hard to get to, pull all 4 plug wires, connect the wires to the plugs with small rubber hose( vacuum tube) the spark will travel thru the rubber hose to the plug, then just touch the hose with a grounded test light or if you don't have one something like a screw driver that's grounded to frame. This will kill the spark to that cylinder. If the rpm drops, that cylinder is carrying, if the rpm stays the same, you've identified a dead cyl. Then just diagnose misfire, you can't mess with the carbs until you've either ruled out a misfire or fixed it.

 

[JakeBoucher]

Sweet thanks, the plugs are easy to get to so I will try that. Here's a photo of the bike!

 

[2strokesteve89]

Sweet thanks, the plugs are easy to get to so I will try that. Here's a photo of the bike!

Nice....replace the seat cover and polish her up, it'll be a beauty. Shoot you straighten out the running problem cheaply you could make a couple bucks off that one.

 

[JakeBoucher]

Thanks, the gas tank has a decent dent in it. I might be able to pull it easy though.

 

[JakeBoucher]

Oh and the seat cover is in good shape, that's just some wiring laying ontop

 

[2strokesteve89]

Oh and the seat cover is in good shape, that's just some wiring laying ontop

Oh yeah, I see that now. By the way, I can't see that dent so well, but you may be able to use pressurized air (not much) to pop that dent out. But be carefull not to go too much.

 

[JakeBoucher]

Oh very good idea thanks. The dent is right next to the fill hole, I'll take a picture of it.

 

[JakeBoucher]

Here's a few photos

 

[2strokesteve89]

Here's a few photos

That is more of a crease than a dent, it may not pop out so easy.if it doesn't come out, maybe just put a matching dent in the other side, make it look like it was meant to be there.........

 

[JakeBoucher]

Haha might have to do that. My grandpa owned a body shop for 20+ years so I'll see what he would do.

 

[SRAD97750]

I have a garage full (nearly a complete bike) of 79 GS750 parts if you are in need of something... My tanks are dented worse than your's though. -BIG DAN

 

[JakeBoucher]

Awesome, thanks Big Dan! I am positive I will be contacting you later on that

 

[JakeBoucher]

So I believe I found my problem. I pulled the gas tank and the petcock as two hoses, 1 for the left 2 carbs and 1 for the right 2 carbs. The right two carbs are connected to the cylinders that are running normal. The left two carbs are connected to the cylinders running hot. Guess what the right 2 carbs fuel line has? A fuel filter... The left two carbs has no filter what so ever. So I am assuming the carbs on the left side are gummed up! Causing lean conditions

 

[JakeBoucher]

Never mind disregard that post. So all 4 of the pipes are hot, I just checked after changing the oil and firing it up. The bike will idle on choke, but dies off of choke. Sounds like it's time for a carb clean! The bike is running on all 4 as well. Seems to still be running a little lean, but I think cleaning the idle circuit should richen it up a tad.