trying to get my bike started

[froldt]

I know I've asked before... but now that it's warm enough to work, I am making the time to actually do some wrenching.

I've got an 82 GS750T that won't start.
I bought her, rode for just over a week, and then she wouldn't start. I thought at first that I was flooding, but... won't start at all. She'll turn over (starter motor) but I don't believe she's firing.

I rebuilt the carbs (to the best of my ability), rebuilt the petcock (a waste of time/money - need to buy a new petcock, got a home-made tank rigged up for right now). Went back and bench-synched the carbs. I've cleaned the kill switch. New oil and filter in there.
Airbox is clean (tried with and with-out filter - both stock and K&N). Checked and set the valves.

There is fuel in the float bowls, but I can't tell that there is any on the spark plugs. I put a shot (maybe not enough?) of starting fluid directly in the #1 Cyl, but still no luck.
There are brand new spark plugs installed, and they fire. (at least num's 1 and 4). I tried the cables in both combinations (1 and 2, and switched), in case I re-hooked them incorrectly, but that made no difference.
The battery is charged. It doesn't hold the charge for a terribly long time, since I'm not doing anything but turning the bike over occasionally, but it holds as well as can be expected.

Umm... that's all I can think of off hand. Any suggestions?

[chef1366]

After trying to start it are your spark plugs wet?
I would check spark on all spark plug wires.
A bad battery will make your life hell trying to start a bike that's been sitting.

[froldt]

After trying to start it are your spark plugs wet?
I would check spark on all spark plug wires.
A bad battery will make your life hell trying to start a bike that's been sitting.

No, I can't tell that the plugs are even damp. However, the plugs are (according to the picture/description in my Clymer manual) carbon fouled. There was a black, soot-like deposit on the plug when I pulled it. It wiped right off, though.

Update - Ok, I tried more ether in cyl #1, and she fired!

Where should the throttle stop screw (on the carbs) be set at, roughly, to get me started? Perhaps I've got it set too low, so it won't even fire/start?


Did some compression testing (first time, so I kinda winged it). Now, keep in mind that she hasn't run in about 4 months, so this was cold. At least it's nice, temp-wise outside.
#1 - 175psi
#2 - 52ish
#3 - 102ish
#4 - less than 50

Does this mean that gas got in the oil and fried the rings?

[bradleymaynar]

Battery? I didn't see you mention it. It could be possible that the battery is just worn out. Typically they're only good for a couple years. )Speaking of which.... ). I'd agree also that you should check the plugs. And buy a manometer (synchronizer) and sync the carbs.

Set the throttle stop up so that the bike starts. If the engine starts to race, kill it and lower the throttle. I believe optimum idle is between 900 and 1200 RPM. For manometer synching it's 3K.

Brad bt

[SqDancerLynn1]

Those compression readings could make it dificult to start. First thing to do is check the valve clearances !!! after that pour some Risolin sp enging treatment/trans fluid/carb cleaner ??? in to each plug hole & let it soak
overnight. Then try and run it, if you can get it to start
left coil should connect to cyl 1&4

[froldt]

Battery? I didn't see you mention it. It could be possible that the battery is just worn out. Typically they're only good for a couple years. )Speaking of which.... ). I'd agree also that you should check the plugs. And buy a manometer (synchronizer) and sync the carbs.

Set the throttle stop up so that the bike starts. If the engine starts to race, kill it and lower the throttle. I believe optimum idle is between 900 and 1200 RPM. For manometer synching it's 3K.

Is bench syncing the carbs not enough to get it started? I know that I will need to sync them later, once she's running, but I was hoping to not spend the money till I do have her up and running.
Battery was only about 6 months old when I got her (which makes it less than a year now).
The plugs all fire. I did go back and check that. They might be a little weak, but I was trying to get her started, so the battery might need a touch-up charge.

Those compression readings could make it dificult to start. First thing to do is check the valve clearances !!! after that pour some Risolin sp enging treatment/trans fluid/carb cleaner ??? in to each plug hole & let it soak
overnight. Then try and run it, if you can get it to start
left coil should connect to cyl 1&4

Valve clearances are good. I checked and set them (twice) when I had the carbs off.
Where do I get the Risolin sp engine stuff?
Hmm... the coil might be hooked up wrong, but I think I hooked it up how it was when I got her. I'll definately check on that, though

[gotjeepzj]

Spray starting fluid into your airbox and start it. If it attempts to run at all it's a fuel or timing issue. If you don't even get a cough out of it, you have spark issues. I've used this for years on mowers, bikes, cars, boats, anything with an internal combustion motor.

[froldt]

If you don't even get a cough out of it, you have spark issues.

Well, I've got spark issues, apparently. Not even a cough...

The lines from the coils are connected to the right places, though. I just never noticed before how they were hooked up.

[bradleymaynar]

Having never done a bench sync I couldn't tell you. But, after rebuilding the 1100's carbs, it fired right off when I got them back on. I think it was a couple of months before I actually synced them properly.

Definitely charge the battery up. If it's been sitting, connected on the bike, It could be likely that it has discharged a bit. This could possibly explain your weak spark.

Brad bt

[froldt]

Had a friend of a friend come over and look at the bike. He said that, based on the compression readings, I need to rebuild (to some extent) the top-end. So... I'm in the process of taking the top end apart and the cam out. Once I've done that (here in just a bit), I'll give him a call and he can come and look at it, measure the cam lobes, and we'll see where to go from there.
Maybe it's just a stuck valve, or a loose one, or something. But... tomorrow I should find out. (Or that's the plan, have him come back over tomorrow.)


By the way, the battery's good to go. I charged her the other day before I started testing compression and everything. After a bunch of starting attempts and sitting for a couple of days, I checked it today, and sitting at just under 12v.
11.85v or something...

[froldt]

Bah, can't get the exhaust off. Twisted a hex wrench about 180 degrees and only got three bolts loose. Going to stop by the store and pick up a couple more, and I finally found the torch. So... hopefully tonight I'll have her apart.

[andrewclaycomb]

Have you checked your timing/points?

[chef1366]

When you get the head off check the valves and valve seats for carbon build up. Especially the one with low compression. If the bike was run for any amount of time with either bad valve clearance or bad valve stem seals than there could be a carbon buildup preventing the valves from sealing. The valve stem seal problem usually only happens on the intake valves since the exhaust valves are hot and burn the oil off so it doesn't accumulate.
You can fix this with a light lapping of the valves JUST to remove the carbon. You don't want to remove any metal from the seat or valve because they have an outer coating of hardener.

[froldt]

Managed to get the exhaust off, and only broke off one bolt. Yay! Anyone need a pretzel-shaped hex wrench?

We did a (can't remember what he called it) drip test? Pulled the head off and poured some gas on top of the valves. None of them held the fluid, so they didn't seal well at all.
The valves and seats were nice and clean. The pistons had some pretty bad build up, though.

With 45,xxx miles, he was surprised at the condition of the pistons. 1 and 4 were in excellent shape. 2 and 3 had just a little bit of scraping on the sides, but the cylinders didn't show any wear at all.

Since I'm planning on having Gertrude for a number of years (hopefully 7 or so, as the main, only?, transportation) I'm going to do a complete top-end rebuild. We could probably just hone the cyls and put new rings on, but I'll go ahead and spring for the complete, so as to have a more reliable bike.
Gotta call around tomorrow and find a good motorcycle machinest.

Where's the best place to order pistons and rings and a top end engine gasket set?

Also, does the cam chain have a master link? If so, I'll go ahead and replace that while I'm in here...