Valve Clearance Problem?

[78gs1000]

Ok, I have a backfire when I run the engine hard, especially at higher rpms about 4-5k range and up. This has not happened before, and just started out of nowhere. Also a noticeable loss in power during acceleration, and its harder to keep it at a certain speed while cruising.

Things I have done, 1. Took apart and cleaned the carbs 2. Checked timing, its good 3. Power to all the spark plugs/coils are good. 4. Resynchronized the carbs.

Just today I checked my valve clearances, the #2 Exhaust shim needs to be changed from a 2.9 to a 2.85. Also on the #2 Intake shim needs to be changed from a 2.7 to a 2.75. #3 Intake shim as well from a 2.75 to a 2.8. All others are within acceptable clearance range.

**Ok there's the info.
***NOW, would the valve clearances on those 3 shims cause the issue reported above? Or do you have another idea for something I could try.

Thanks!

[SqDancerLynn1]

I don't think so but what were the actual clearances ?? May need to further clean the carbs ? Could have a weak valve spring, a damaged exhaust system ???

[78gs1000]

I don't think so but what were the actual clearances ?? May need to further clean the carbs ? Could have a weak valve spring, a damaged exhaust system ???

Ok, my clearances are as follows: (In MM)
Exhaust ** 1- 0.05 ** 2- 0.025 ** 3- 0.05 ** 4- 0.05
Intake ** 1- 0.075 ** 2- 0.1 ** 3- 0.125 ** 4- 0.05

As you can see the intake 2, especially 3 is pretty off. Exhaust 2 isn't too bad.

[78gs1000]

Just an update, rechecked the carbs, the pilot fuel screws tips got broke when I put that back, but I don't notice any differences and the same problem is occuring.

** So is this a valve clearance problem?

I am going to order the shims I need tonight as well as the valve decompressor tool from Z1 Enterprises. Let yall know what the outcome is

[Steve]

Save your money on 'the tool', just use zip-ties.

Some claim to be able to use 'the tool' successfully, I'll believe it when I see it.

If it were my engine, I would DEFINITELY change that exhaust shim, but leave intake #2 as-is. #3 is loose enough that it should be changed.

.

[78gs1000]

Thanks Steve, I looked up the "zip tie" method and really just don't understand it... You fold it over, crimp the part you folder about an inch from the end, and then hook it on the valve through the spark plug hole? I wish I knew someone that lived nearby the area to show me

[BassCliff]

Hi,

I don't think your issue is related to valve clearances. Although I am not a zip tie apologist, the clearances should be set to the correct specifications. I run mine on the loose end of spec. As of my last adjustment, all of my clearances are in the 0.07 - 0.11 mm range. Sometimes I'll even swap out a shim on a 0.05 mm clearance to get 0.10 mm. But that's just me.

Providing the carbs are properly cleaned and adjusted, I would lean toward an ignition issue with those symptoms. Do you have the stock ignition? Is the spark advance working properly? Do the coils spec out? Have you tried installing new points and condensers? Have you insured the points are clean and properly gapped?


Thank you for your indulgence,

BassCliff

[78gs1000]

Ok BassCliff to answer your questions, Do you have the stock ignition? No I have aftermarket. ** Is the spark advance working properly? Yes, i am getting a fluent reading of power from the spark plug and coming out of the ignition, spark advance. ** Do the coils spec out? What exactly do you mean spec out? They are giving an accurate power reading. Have you tried installing new points and condensers? No I haven't but the ones I have are tested power wise to be functioning. ** Have you insured the points are clean and properly gapped? You mean spark plug gaps? They are all within range.

[78gs1000]

If this doesnt clear up the problem, I am gonna look into checking out my valve springs as SqDancerLynn1 mentioned.

[Steve]

Thanks Steve, I looked up the "zip tie" method and really just don't understand it... You fold it over, crimp the part you folder about an inch from the end, and then hook it on the valve through the spark plug hole? I wish I knew someone that lived nearby the area to show me

That's pretty much it.

After measuring your clearances and recording them (by the way, I know a guy that offers a dandy way to do that ), rotate the cam so the valve is fully opened. You can see the edge of the valve through the spark plug hole. Slide the folded end of the zip-tie under the edge of the valve, rotate the cam so it's pointing away from the valve. You now have enough room to move the bucket around to find the notch, then lift the shim out for inspection and/or change. Insert the shim, make sure it's fully seated, rotate the cam, pull out the zip-tie, move to the next valve.

I have had 'the tool' slip sideways off the side of the bucket too many times to be comfortable with it.
Had it happen on one of my previous Kawasakis, and this was the result:




It took about an hour of fishing with a magnet and another hour of assembling the jigsaw puzzle before I was comfortable turning the crank any more. I figured that small chip on the back side was not going to present enough of a problem to worry about, so I continued.

After having the Suzuki tool slip off the edge of a bucket and seeing how easily it did so, I switched to the zip-tie method and have enjoyed valve adjustments ever since.

.

[78gs1000]

Ok, so everything has been done, and its running FABULOUS all the way until I hit 5500rpm. then the engine gets really loud and I have to really force her to go higher. Is that a sign of weak valve springs? Or what else?

[Nessism]

Not valve springs. Lean mixture or weak spark would be my guess.

[78gs1000]

Hmm possibly a lean mixture, it's still wanting to backfire slightly until its heated up some then I hardly notice it, if I have a helmet on I don't notice it.
As far as the spark goes, everything there checks out fine.

[rustybronco]

I suspect if you put your fingers in your ears you wouldn't be able to hear it either; but that doesn't make the issue go away.

[78gs1000]

I suspect if you put your fingers in your ears you wouldn't be able to hear it either; but that doesn't make the issue go away.

Haha, thanks, ill try that