Vacume line blowing air instead of sucking.

[dgeorge]

Well I recently rebuilt the top end of my 83 GS1100GK, after getting everything back together it cranked up and I rode for about 15 miles. It wasn't returning to idle as quickly as it should so I thought that I might have put the wrong jets in the carbs when I rebuilt them (kits came with 2 different sizes for each). So I took them off and sure enough I had the wrong jets in them so I made sure I replaced them with the proper ones 115 mains 40 pilots and 170 air pilots (had the 107mains and the 160air pilots). After I reinstalled the carbs I could not get it to start. I've had the carbs off and on so many times now I've lost track, I've redipped them and blown out all of the passages with compressed air. Still nothing so I unpluged the vacume line (I'm using a lawn mower tank so have it plugged) and it is blowing air out instead of having a vacum. I've also checked and it is getting a good spark. It seems like it tries to start sometimes, but just won't kick over. Anyone have any ideas on this? I'm going to run compression check later this afternoon (have some errands to run), and probably pull the cam cover back off to check the valve clearance again, (did it once after it wouldn't start the first time and double checked the timing also). Sorry for the long post, but this has me baffeled. Thank you in advance for any advice or assistance.

[earlfor]

Re: Vacume line blowing air instead of sucking.

Hmmm, thats a strange one. :-)

Do I have this correct? The bike gas tank is not installed. You are running the engine from a lawn mower tank and the vacuum fitting on the carb that normally runs to the petcock with a hose is plugged/capped off.

I assume you have a gas line directly from the lawn mower tank to the carb nipple?

Earl

Well I recently rebuilt the top end of my 83 GS1100GK, after getting everything back together it cranked up and I rode for about 15 miles. It wasn't returning to idle as quickly as it should so I thought that I might have put the wrong jets in the carbs when I rebuilt them (kits came with 2 different sizes for each). So I took them off and sure enough I had the wrong jets in them so I made sure I replaced them with the proper ones 115 mains 40 pilots and 170 air pilots (had the 107mains and the 160air pilots). After I reinstalled the carbs I could not get it to start. I've had the carbs off and on so many times now I've lost track, I've redipped them and blown out all of the passages with compressed air. Still nothing so I unpluged the vacume line (I'm using a lawn mower tank so have it plugged) and it is blowing air out instead of having a vacum. I've also checked and it is getting a good spark. It seems like it tries to start sometimes, but just won't kick over. Anyone have any ideas on this? I'm going to run compression check later this afternoon (have some errands to run), and probably pull the cam cover back off to check the valve clearance again, (did it once after it wouldn't start the first time and double checked the timing also). Sorry for the long post, but this has me baffeled. Thank you in advance for any advice or assistance.

[dgeorge]

Do I have this correct? The bike gas tank is not installed. You are running the engine from a lawn mower tank and the vacuum fitting on the carb that normally runs to the petcock with a hose is plugged/capped off.

I assume you have a gas line directly from the lawn mower tank to the carb nipple?

Yes that is correct.

[earlfor]

So instead of the cylinder behind the carb with the vacuum to petcock fitting drawing intake air, it is expelling air into the airbox? I would check compression. Also, just for the hell of it, I would remove the carb stack and hold my hand over each rubber intake boot while cranking the engine just to be sure each cylinder in drawing air and sucking my hand down onto the boot. If one or some are blowing air out, the only thing I can think of that could cause this is piston ring blowby and compression is escaping down the bore, past the rings and exiting through the carb intake boots. If this is happening though, the crankcase oil should show aeration and be a whipped muddy whipped cream consistancy too.

Do a compression check and a "hand" check and lemme know.

Earl

Do I have this correct? The bike gas tank is not installed. You are running the engine from a lawn mower tank and the vacuum fitting on the carb that normally runs to the petcock with a hose is plugged/capped off.

I assume you have a gas line directly from the lawn mower tank to the carb nipple?

Yes that is correct.

[dgeorge]

Thank you for your input Earl. I'll do the compression check and hand over intakes when I get back this evening. I've got to go get a router/firewall for this computer since I put it back on the internet. Just had to brake into my garage. I left my keys in the bikes ignition and locked up the garage and didn't have a spare so I've got to get a spare made also while I'm out.

[focus frenzy]

UMMM, Earl, the 1100GK is a four stroke engine, not a two stroke.
blow by past the rings to the crank case can not blow out the intake.

the only things it could be is,
A= the intake valve is not closing allowing the air to escape back past the intake valve and out the intake port
B= the intake cam has jumped time and the intake valve is opening when the piston is coming up instead of when the piston is going down.
you did say you just rebuilt the engine?
is it possible you may have not loosened the lock screw on the cam chain tensioner, allowing it to take up the slack?

[earlfor]

Thank you Leon. Ummm DUH, sometimes I think I'm losing my mind and then along comes someone to confirm it. :-) I guess it aint no H-1 eh? :-)

Earl

UMMM, Earl, the 1100GK is a four stroke engine, not a two stroke.
blow by past the rings to the crank case can not blow out the intake.

the only things it could be is,
A= the intake valve is not closing allowing the air to escape back past the intake valve and out the intake port
B= the intake cam has jumped time and the intake valve is opening when the piston is coming up instead of when the piston is going down.
you did say you just rebuilt the engine?
is it possible you may have not loosened the lock screw on the cam chain tensioner, allowing it to take up the slack?

[dgeorge]

Well I think Leon was partially right, I think the timing is off. I've posted a new topic called timing a GS1100GK. If someone would kindly look at the pictures I've posted and clarify which position is correct I would greatly appreciate it.