Compression and throttle question

[JTGS850GL]

I have already reached out to Ray about shims, thanks. How do I tell if the valves and seats are burned?

The best way to verify valves is, after you've completed the adjustment procedure, do a compression and/or leak down test. If you have a burnt valve the compression will be low and you'll have excessive leak down. If the compression tests are bad then add a teaspoon of oil to each cylinder and do the test again. If the numbers come up then it's rings. If no change in compression figures then the valves are the problem.

Compression tests are easier to do but a leak down test will not only tell you that you have a problem but will also tell you where the problem is by listening to where the air is escaping. If you hear the noise in the intake or exhaust then valves are suspicious. If the sound is in the crankcase then rings. Don't forget to do the leak down test with each cylinder at TDC.

[Ian Donahue]

Embarrassing update: So... I thought all my valves were too tight because my .03mm feeler was stuck to my .04mm feeler (tell me you've never done it!). With a remeasure, 7 out of 8 are good, between .03 (I4) and .08 (I2+ I3). E4 is below .03, but my "feel" is that it is just below. So I will fix that one. I do not need to fix the other ones right? .04 and .04 are within spec, so that shouldn't cause my idle issue.

Question: I got this from another post:

Exhaust lobe on #1 facing forward: check E1 and E2
Exhaust lobe on #4 facing forward: check E3 and E4


Intake lobe on #1 facing perpendicular: check I1 and I2
Intake lobe on #4 facing perpendicular: check I3 and I4

Why so finicky? Why not just check each valve one at a time with the lobe perpendicular to the shim?

Anyhoo, looks like I'm narrowing my issues to the carb, but at least I can swap out the one shim and button it up (with my new reusable gasket that is coming on Monday!), and continue with the Bikecliff carb rebuild. Any thoughts?

[Steve]

Why so finicky? Why not just check each valve one at a time with the lobe perpendicular to the shim?

There are two reasons for this, one is the happy coincidence of convenience, the other is much more important.

You will note that in those positions, neither valve on that side of the cam is being depressed. That will keep the cam in a more or less neutral position in the bearing. There is a very slight clearance in the bearing to allow oil flow. If you push the cam sidways by depressing a valve, it might give you a false reading at the other valve.

.

[Ian Donahue]

There are two reasons for this, one is the happy coincidence of convenience, the other is much more important.

You will note that in those positions, neither valve on that side of the cam is being depressed. That will keep the cam in a more or less neutral position in the bearing. There is a very slight clearance in the bearing to allow oil flow. If you push the cam sidways by depressing a valve, it might give you a false reading at the other valve.

Totally right again Steve. With this technique, each valve was about .01mm - .02mm tighter, so I now have a more accurate spec. Ray hooked me up with new shims and I'm hoping to get them before the weekend and get this buttoned up. I bought this thing for my 50th birthday (Saturday) and I'd love to see it run right for a birthday ride!

[Ian Donahue]

Update #3: I am dutifully following the carb rebuild outlined on the bikecliff page. For the float needle seats, I found this:

float seat.jpg

So if you can't see it, there is a thick hard gak on top that is blocking the passage of air (or gas obviously). That is #4. #3 looked the same, the separated gak next to it is from #3. During this whole process #3 and #4 were not warming up like 1 and 2, maybe there's a connection? :-)

Anyway, on the carb rebuild PDF, the picture shows a half-dome screen under this piece. I don't have that on any of these. Is it required?

Thanks again for the help so far. How come no one told me to do the carb clean the right way? ;-)

[Nessism]

You have aftermarket float needles and seats.

[Carter Turk]

That o-ring doesn't look like the o-rings were replaced recently as stated in 1st post?

[Ian Donahue]

That o-ring doesn't look like the o-rings were replaced recently as stated in 1st post?

That is the next step. I have the kit from Cycleorings.com, and I will be replacing all these. Any opinions about the screen you see on the bottom of the seat in the PDF? I don't have those, are they necessary?

[Ian Donahue]

That o-ring doesn't look like the o-rings were replaced recently as stated in 1st post?

Ah, now I see what you mean about my first post. In the throes of my newbie-ness, I did a light carb cleaning and replaced *some* of the o-rings with the rings that came in a 3rd party carb rebuild kit. Now that I am older and wiser, I purchased the recommended cycleorings kit and I am working through the tutorial. The lacquered gasoline on the bottom of the seat is yet another argument for taking ALL OF IT APART! I'm doing it right this time, and I have high hopes for a smooth running bike by the end of the weekend.

[Ian Donahue]

You have aftermarket float needles and seats.

Can you point me to the proper OEM seats and needles? I found this one on bikebandit...

http://www.bikebandit.com/aftermarket-parts/motorcycle-fuel-and-air/carb-kits-parts-accessories-universal/mikuni-needle-valve-for-square-pump-super-bn-carburetors?m=13984

...but I'm not sure it's right since it does not look like the aftermarket seat I took out. The 34 year old schematic on sites like partszilla are not that helpful.

[1948man]

There is a good chance you can get them from a member here. Chef often has things like that. You could post in the parts wanted section. I have run carbs without the little screen filter but they are cheap at PartsOutlaw.

[Ian Donahue]

Update #4: things are going well. I have the carbs mostly back together, I discovered (due to the excellent tutorial) that the vent passages in 2 of my bowls are clogged, so back into the dip for the night. A new question: I am adjusting the valves, so I have the valve cover off. ONE of the 19 bolts is longer than the others. Does anyone know where this bolt goes?

[1948man]

On my '83 1100g, the one longest bolt is on the front row, 3rd from the left. Not sure yours will be the same. My bolts are of several lengths and it is important to get them back in the right places.

[Ian Donahue]

Update #5: OK, I adjusted my valves (thanks Ray!) and finished the proper bikecliff carb rebuild tutorial. Well, it seems a little better, but the idle still climbs up into the 4000s after about 7 minutes of idling quite nicely. I decided to go ahead with the carb syncing, so I hooked up my brand new Morgan Carbtune and... nothing. The engine does not seem to be lifting the bars. If I blip the throttle, it will jump up for a second and then go back down again. #1 is jumping a little, but the other 3 are sitting on the floor. Is this related to my low compression issue? I have about 60 pounds in each cylinder. Do I have a bad head gasket?

[Ian Donahue]

Update #6. So the bike is still acting up with the rising idle and a lot of popping. So I tried the starter fluid trick to find the leak (I have replaced the o-rings and intake boots). I couldn't find it, but as I worked my way lower I found a definite response to the starter fluid where the head meets the crankcase, almost all the way around, some places more than others. This means the head gasket is blown, correct? That's replaceable, right? I just have to take the whole thing apart right?