Checking top-end while on frame

[Guest]

I'd like to remove the top to clean the piston heads. I took a look into the spark plug holes, and it looks like there's some buildup there.
The manual appears to say I can do it without unmounting the engine from the frame. It looked to me like there wasn't enough space between the top of the engine and the frame. Is that possible?

 

[hampshirehog]

Yes, there's enough room to remove the head with the engine in the frame. If you're taking off the head you might loosen off the cylinders and create a base gasket leak so best to pull the whole top end while you're at it. Use genuine gaskets only to reduce the risks of leaks on reassembly.

Or you could save yourself a load of bother if you only want to clean off carbon build up. Try your favourite brand of engine cleaner and see how things go.

 

[Rich82GS750TZ]

Just an opinion, ZPS. I would expect to see a certain amount of carbon buildup on top of the piston. Not sure if that's reason enough to do a full top end job. If you disturb the head, conventional wisdom on the forum is that you definitely need to replace the base gasket too. So that mean the cylinders are coming off. While you're in there, may as well do rings. Then you'll be thinking, while you've got the head off, may as well replace valve seals and lap the valves and seats.

Again, my opinion, unless you have compression issues or an oil leak, leave the head alone. Check and adjust your valves on a regular schedule, and ride your bike.

 

[Nessism]

Some carbon on the pistons is normal. I would not pull the top end apart for that.

 

[Guest]

Alright, thanks. I pulled the spark plugs out and replaced them all with new ones ($2 per plug, why not?). These are the ones I removed.

I've taken the carburetor apart 3 times, and it looks pretty good. The only problem is that I haven't been able to unscrew the gang plate without stripping the screw heads. They're all wedged on there.
I've gotten the bike to run a couple times. Ordered a couple new ignition coils. The ones that are on there seem to be rather wonky. Once is an original that didn't seem to make spark, the other is a newer one that's got a weak spark.

 

[Rich82GS750TZ]

Could be running rich. Check that your air cleaner is clean, AC box is getting air, not blocked.

 

[Steve]

I've taken the carburetor apart 3 times, and it looks pretty good. The only problem is that I haven't been able to unscrew the gang plate without stripping the screw heads. They're all wedged on there.

If you haven't gotten the gang plate off, how have you taken the carburetor(s) apart? :-k

How much have you actually taken off of the carbs?
How much "cleaning" did you accomplish?
Has overall performance improved?
Is the performance CORRECT yet?

What coils did you order? Hopefully they are correct for the bike.
I mention this from experience. My wife's bike came to us with Accel coils, which are a nice upgrade. However, the bike seemed to eat an ignitor every couple of years. I finally did some troubleshooting and found that the coils had 0.7Ω primaries, which is WAY too low. Replaced them with proper 3.0Ω coils.

By the way, reading spark plug color is virtually worthless, unless you know what the engine was doing JUST before the spark stopped. Which carb circuit was in operation?

.

 

[Guest]

If you haven't gotten the gang plate off, how have you taken the carburetor(s) apart? :-k

How much have you actually taken off of the carbs?
How much "cleaning" did you accomplish?
Has overall performance improved?
Is the performance CORRECT yet?

What coils did you order? Hopefully they are correct for the bike.
I mention this from experience. My wife's bike came to us with Accel coils, which are a nice upgrade. However, the bike seemed to eat an ignitor every couple of years. I finally did some troubleshooting and found that the coils had 0.7Ω primaries, which is WAY too low. Replaced them with proper 3.0Ω coils.

By the way, reading spark plug color is virtually worthless, unless you know what the engine was doing JUST before the spark stopped. Which carb circuit was in operation?

.

The carbs have tops and bottoms. Took those off. Took all the jets out, except for a needle jet that was stuck. Took off the float needles, all looked good. No nicks, gouges, or dirt.
I soaked the jets in vinegar for a day, then poked through all the holes with a sewing needle until I could see light through both sides. Sprayed the carb body interior with carb cleaner.
The issue is getting it to run, so the performance has been about the same.
I have no carb syncing tool, and that's a bit outside of what I can currently afford, at least possibly until next month.

I ordered these: https://www.ebay.com/itm/264414925007#vi-ilComp
They resemble one of the ignition coils that was already on the bike. One was the old grey cylinder, the other looked like one of those.

 

[cowboyup3371]

You did not clean the carbs then as there are passages in them so small they can plug easily. You'll need to do it again and take the plates off; use some PB Blaster to help loosen the corrosion holding the screws in place.

 

[Guest]

I have. They still aren't budging.

 

[cowboyup3371]

Do you have an impact driver? You can pick one up from Harbor Freight fairly inexpensively but you'll need to get different screw heads as they are very cheaply made

 

[Brendan W]

If the screws are original they could have JIS heads and a Phillips or other will chew them up. JIS tools are available from a number of sources.