Won't start in the cold.

[Anonymous]

Hi guys,

I'm having a cold-start problem with my 1980 GS750L. Works great most of the time, fires right up. But when its below about 8C(I think that's 45F), it just won't start. It turns over ok, but nothing else. Gas is getting to the carbs. And if I try again when its a little warmer, no problem.

I park in a garage, so its dry. What could be causing this? More importantly, how to fix? Its a nice clear day today here (but cold), and I can't ride

Thanks

 

[daveo]

Most of time when I've had an engine with this problem,(assuming everything else is OK) it turns out to be low compression from the rings going bad, seems the temperature drop is enough to cause the pistons and rings to shrink to the point where it just isn't making enough compression. Sometimes if you keep rolling it over, the friction generated will heat and expand them enough to get it to fire. Do a dry compression test, then add a teaspoon of oil to each cylinder and retest, if the compression comes up 20-30 lbs. when wet, you've found the problem

 

[SqDancerLynn1]

First thing to check would be the choke cable adjustment, then the choke enrichment circuit of the carbs. I also put the petcock on prime for a few seconds to make sure the carbs are full before trying to start

 

[Eliseo Monteverde]

I?ve the same problem in my "baby kat".
I dont know why, Carbs are clean and I asume that the choke system is ok .
It help me two things:

1-A little "fuel injection" inside the cilinders by a syringe and the full choke.
2 -Leaving the petcok in prime position some hours before start the engine.
As soon as the engine starts, return to on position.

I recommend last option only if you have a fuel filter made of papper betwen the petcok and the carbs.

Good luck
:wink:

 

[Anonymous]

How long does it take to swap out the rings on the pistons? and how difficult of a job is it?

--Tyler

 

[Anonymous]

How long does it take to swap out the rings on the pistons? and how difficult of a job is it?

If you are asking - it's probably going to be a fairly big job.
Get a manual and read it - maybe 10 times - in the correct sections. You will have to not only replace the rings, but hone the cylinders, replace the gaskets in the path, clean parts, possible valve job, clean parts (in there twice for emphasis), and a bit more. Too much to list a step-by-step procedure, Thats' why you need the manual and you need to read it to become familiar with what you are going to do.

If you have any questions after you read the manual, ask away. Someone in here will be able to answer.

I'm not trying to be a smart a$$, really.

Oh, how long and how much - almost forgot. If you are good at it, and you are looking at 4-8 hrs labor - not counting any head work - or cleaning. Cleaning parts always kicks my butt.

How much - gaskets and rings - maybe $100 - headwork not included or price for honing the cylinders. You might be able to do that yourself.

 

[KEITH KRAUSE]

WarrenC, as mentioned, you may have a ring problem, but it could be something simple to check.
Is the choke cable slack OK?
Are your sparkplugs in good condition and the correct heat range?
Check/adjust the plug gaps.
Make sure you have good connections at the coils/leads/plug caps.
Is the battery in good condition and the level correct?
Have the pilot/mixture screws been moved?
Do you try different amounts of choke?
Do you open the throttle at all when it does'nt want to start? Doing this actually by-passes the choke circuit.
You may have to clean out the choke circuits.

 

[Don Lobacz]

Weak spark is a good guess. When I put Dyna coils on my bike, the only noticeable difference was COLD WEATHER STARTING.

 

[mdole]

First thing to check would be the choke cable adjustment, then the choke enrichment circuit of the carbs. I also put the petcock on prime for a few seconds to make sure the carbs are full before trying to start

I agree with the above but also wanted to add that my 1981 GS750L gets real touchy about starting under 20F. I put on full choke and when it starts I need to crack the throttle slightly and get it of come up to about 3000 rpm momentarily to clean it out and then it will idle. If I don't do this is will only idle for a few seconds then load up and die.

Mike

 

[Anonymous]

Thanks for all the help guys. My spark plugs seem to be in good shape. I need to pickup a compression tester and then wait for some cold weather again.. its running great now. I hope its not anything really serious like rings. :wink:

 

[mdole]

How long does it take to swap out the rings on the pistons? and how difficult of a job is it?

If you are asking - it's probably going to be a fairly big job.
Get a manual and read it - maybe 10 times - in the correct sections. You will have to not only replace the rings, but hone the cylinders, replace the gaskets in the path, clean parts, possible valve job, clean parts (in there twice for emphasis), and a bit more. Too much to list a step-by-step procedure, Thats' why you need the manual and you need to read it to become familiar with what you are going to do.

If you have any questions after you read the manual, ask away. Someone in here will be able to answer.

I'm not trying to be a smart a$$, really.

Oh, how long and how much - almost forgot. If you are good at it, and you are looking at 4-8 hrs labor - not counting any head work - or cleaning. Cleaning parts always kicks my butt.

How much - gaskets and rings - maybe $100 - headwork not included or price for honing the cylinders. You might be able to do that yourself.

If you were going to replace the rings you would probably also want to do a valve job.

What it would take for the ring replacement would depend on what you find when you check the cylinders. If they are scored you will need to bore the cylinders and if that is the case then depending on how much you change the bore either replacing pistons and rings or going to oversized rings. If the cylinders are good then you should be able to hone them and you may need to remove a ridge at the upper end of the cylinders. I wouldn't use a ridge reamer unless you have used one before they are self centering but if you do not set it up and center it right it can do major damage. Honing the cylinder is pretty easy if you can find a hone that attached to your electric drill it is no big deal but you need to read how to do it to get a diamond cross thatch pattern so you really need a manual.

If you pull the heads and take them to a shop and have the valve job done that saves quite a bit of the cost and taking the cylinders into a machine shop to be bored isn't saves the disassembly labor. If you only need to hone the cylinders any small engine repair shop should be able to do it for you usually for a lot less money that a motorcycle shop would charge as their labor rate is usually less than half and maybe closer to a third the motorcycle shop rate.

I have a friend with a small engine repair shop who does chain saws lawn mowers and such and I occasionally will take cylinders to him to hone on some of our bikes. Other things that I have done is stripped carbs and taken the bodies in to him to dip, had master cylinders honed, and had air cleaners made out of bulk foam (this was for bikes that basically used flat elements with foam in a metal frame).

There are a number of ways to save money when working on your bike but you need to keep in mind what can go wrong and what the consequences are. For example putting a gouge in a cylinder basically ruins the cylinder so at least until you feel confident in doing some of the machine work its is better to have someone who is experienced do the work.

None of these things are really very difficult but may are performed more easily when the proper technique is known and that can easily be gained by watching someone else do the tasks such as ridge reaming and honing. Hand lapping valves is also something that is not done that much any more but is a good skill to acquire and the consequence of failure is not so bad as you may need to replace a valve but it would be hard to destroy a valve seat.

The best way to learn is to find someone who is knowledgeable and do the work with them. Even if you need to pay someone to do the work with you the possible mistakes that you don't make can more than offset the costs.

Mike

 

[mdole]

I just thought of a better example of the value of experience.

Last winter I replaced a clutch on a Dodge Colt Vista Wagon and it took me three days of lying on the ground struggling to get the transaxle out. The transaxle and transfer case fit in so tightly that it was really hard to get to anything and the manual I had didn't adequately describe how to drop the transfer case. So I started the job working blind even though I had changed a lot of clutches I had never done one on a Colt or even a front wheel drive 4X4 other than on a Subaru.

I fought with it for hours on the second day and finally realized that I had missed a bolt that was hidden on the rear of the engine between the engine and the firewall. It took several extensions and u-joints to get a socket on the bolt and when I finally got it loose the transaxle separated from the bell housing. I then spent a day trying to jack, wedge, pry the transaxle off of the bell housing to drop it out under the car. I finally got it and the next evening spent about 4 hours putting the clutch in and putting everything back together.

Now I could probably drop the transaxle in about 4 hours rather than three days because I learned what it takes to get it loose and discovered the technique for shoe horning the transaxle in and out as it is an extremely tight fit.

If I had had some one knowledgeable helping me with the job I could have had it done on the Saturday that I started working on the car rather than a Tuesday night at about 10:00 pm. So that would have been a really big savings for me in time. The good things about doing the job were that I learned what it took to do it and that I didn't break anything in the process.

Mike