1981 750E - Does not fire when cranked.

Hey everyone,

Looking for some advice on where to start working a problem. I've looked at a lot of posts but haven't found my exact sequence of events or can't try some of the fixes because the bike won't start. If anyone has some suggestions, I'm open.

1--YEAR AND MODEL
1981 GS750E

2--MILES ON ENGINE
Unknown. Odometer cluster hadn't worked for the previous owner.

4-WHAT RECENT WORK WAS DONE TO ENGINE--ETC.

None to my knowledge. The previous owner had it as part of 16 bike collection. He rode each bike occasionally to keep them fresh. I found a trickle charging lead on the battery so I believe him when he said he kept them charged. He said he rode it the day it was picked up.

The Story.
I bought the bike from another state and had it delivered. It ran fine the first night. The next day I rode it to get the title done and to work. I work about 25 miles from home. I noticed it running rough as the RPMs hit 5000 once I got a distance from home. After that started, it seemed to have a varying amount of weakness at different points in the power band. I stopped at a dealer to ask if they work on bikes that old. They said yes. The mechanic wasn't completely sure what the issue was but based on my description, he was thinking carbs. He said step one is to pull the plugs to check their condition.

On the way home, about 14-15 miles from the dealer, the bike shut down. It felt as if I had hit the kill switch or turned off the ignition. Absolutely no reaction when the throttle was opened. I pulled around the corner and it died. No start. Sat there for about 2 min and then it grudgingly fired back up. I got it home.

I left the bike sit for exactly 1 week. It started right up and felt fine initially, enough that I thought about taking it to work the next day. It continued to run well for about 15 miles and then started sputtering and losing power. Eventually it came to a halt as if I had turned off the key. The starter would barely turn over at this point and got no better as it cooled. I trailered it home.

This weekend, with a printed copy of the Stator papers in hand, I started looking at the problem. The battery was only half full of water and under 12 volts. I decided the cost of a Wal-Mart battery was tolerable to ensure I had a good battery. I followed the proper battery init procedure. The sucker cranks like mad now but no fire. The battery checks out at around 12.8V and drops about .5 volt with the ignition on.

I looked through the old Q&A and have some idea of what to do but not sure where to start. Is there something I could have done to screw up the spark by replacing a battery. I only disconnected the battery leads and was vary careful about not touching the tools to any other parts of the bike. I turned the headlight off, I flipped the kill switch, etc... still no fire. I tried the various petcock positions, no change. And yes, it has fuel.

My initial thought is to pull the plugs, check their condition and then do a spark test. What's the best way to do a spark test?

Thanks in advance.

Todd "Woodsie" Woods
1981 GS750E

Hang on a minute, Woodsie ...

Hey gang, check out this new guy.
This is his THIRD post.
He has his location in his profile.
He has his bike in his sig line.
He posted a picture of his bike in his FIRST post.

I think the new guys are catching on. :clap: :clap:


OK, Woodsie, back to your question:
Since the starter is turning, we can assume that your ignition fuse is good. It does not actually power the starter, but the power to signal the starter solenoid does come from that fuse. You have a spare spark plug? Pull one of your plug wires, put it on the spare plug and lay it on the head so it's grounded. Crank the engine to see if you have spark. If not, you will have to go through the ignitor tests. With a sudden shutdown like that, I would not suspect fouled plugs, but it can't hurt to check them.

.

Not to sound ig'nit, but does it have to be the right plug to check spark? Any reasonably close plug should toss a spark right?

woodsietx said:

Not to sound ig'nit, but does it have to be the right plug to check spark? Any reasonably close plug should toss a spark right?

Click to expand...

any plug should work, you're just looking for spark to rule out that problem... you can always just pull a plug as well and use that one if you don't have a spare around.

Having not done much of my own troubleshooting in the past, I want to confirm a couple things before I toast something.

I downloaded 3 manuals from BikeCliff's site. The pictures in the GS750 one are a bit dark.

Question #1: Are the GS750E and GS1100E similar enough to use the pictures in the 1100 manual to locate the various pieces I'm working on? Like the ignitor, R/R, etc...

Question #2: What other service manual (Clymer, Haynes, etc...) is up to the task of helping a fairly new DYI repairer?

My basic plan is to pull the plugs and check their condition. I probably should have a set of new ones purchased before I start huh?!? If the plugs look ok, I'll do a spark test. That test I have figured out. If they don't spark, I will do an ignitor test. This test not so sure on.

Question #3. The ignitor is inside the right side frame cover and should have a blue and green wire coming into it from the right side of the motor?

Question #4: I do not, at this point, need to remove right side cover from the motor?

Question #5: Is it likely both coils may have failed at the same time? Can they be tested without removing them? If not, where are they?

If it passes, I'll start working the other two things, fuel and air.

Question #6: Would having the airbox out lean it out so much the bike won't fire?

Thanks in advance.

Could it be a gas cap vent problem? Next time it dies on you, pull the gas cap and listen for a 'sucking' sound.

1981 Suzuki GS750E that won't fire.

I made it back to the bike this morning. New plugs in hand. Battery was still at 12.44V. I hadn't charged it since my last attempt to start it. I put it back on the trickle charger while I came in to type this up.

The mechanic I talked to on Thurs suggested I give it a spritz of starting fluid to see if it would fire. I was a little hesitant. His thought was if I'm not getting fuel, that would confirm it. He understands that I might have to take it into him for repair and is sympathetic to my desire to eliminate some things to save on money. He thinks it's clogged jets.

I went ahead and tried the fluid. The bike fired right up. It burbled for a few seconds and stopped. Tried it again with the same results.

Next I switched the tank over to prime, won't start. Took the gas cap off and it won't start or stay running. I peeked into the tank with my lighter (not really ha ha) and I can see no fuel but I hear when I shake the bike. I put over 4 gal in it the first morning and have run it less than 100 miles. It seems a bit low, THe tank appears to have a light grey coating in it.

So i'm kind of unsure where to go now. I figure that draining the float bowls will tell me if the petcock is open without having to drain the tank. I don't have the facility for that right now.

I don't want to tear into the electrics if I don't have to. I've seen all the tips on here and plan to go through the bike completely over time. Right now I just want to get it running.

Love to hear thoughts on the issue.

Woodsie

Here's what I found when I pulled the plugs and the float bowl plugs.

I tried a spark test and they all seemed ok. I'm not an expert at spark. I replaced the plugs as is. If I have to take the bike in, I want the mechanic to see their original condition. Plus I didn't have a gapper to ensure the news one are gapped right.




The second two pictures are the float bowl plugs. The sediment n the little container mostly came out of #1. #2 had some initially as well but not as much. Looks like my carbs are filthy.




The petcock checked out when turned to prime. Got a solid stream into the bottle. I didn't get anything to come out of the bottom of carb #1 once I turned it on prime. I believe I should have??

I have a couple more items of concern. I'm not sure how the image thing works so I'll post another message.

Woodsie