valve clearance after head was re-worked 83 gs650g

[DAVE KATO]

Is it routine to have to adjust/change tappet shims after a valve job on 83 gs650gt? The manual I have says the tappet clearance should be .003--.008mm, is this correct? sounds a little skinny. When I re-assembled the head, timed the cams with the crank, it all line up but I had no compression. The valves are remaining open/not completely sealing? well I'm new to the forum, my name is DAVE KATO and thanks for any help in advance. don't ya just love motorcycle people?

 

[Nessism]

Dave Kato,

Yes, adjust the valves. The spec is .03-.08mm, you are off by a decimal point.

 

[DAVE KATO]

Thanks ed .

 

[Steve]

Is it routine to have to adjust/change tappet shims after a valve job on 83 gs650gt?

There are a couple of issues with that statement.
1. What was done during this "valve job"? If they changed or reground the valve seats, yes, you will have to change the shims. The bad news is that you have no idea how much to change, so order ONE of the thinnest size shim to see if it fits. If it does fit, you should be able to measure how much extra room there is and then determine what size shim you will need in that spot. Even worse news would be if the thinnest shim does not work, you will have to open up the engine again and have the tips of the valves ground down a bit (0.01mm) so that you can use stock shims.
2. I don't believe that an '83 GS650GT exists. There is an '83 GS650G, but the T is the letter for the '81 model year. An '83 would be a GS650GD.

The manual I have says the tappet clearance should be .003--.008mm, is this correct? sounds a little skinny.

You are correct in thinking that is a little skinny because your decimal is in the wrong place. The clearance is 0.03-0.08mm. Some of us use INCH feelers to check clearances, those would be 0.0015-0.003". You have to be VERY careful with your measurements. As you can see, both of those specifications have a value with a 3 in them. One happens to be the maximum clearance, the other one is minimum and there are a different number of zeros between the decimal point and the 3.

When I re-assembled the head, timed the cams with the crank, it all line up but I had no compression. The valves are remaining open/not completely sealing?

Yep, sounds like the seats were ground, letting the valves sit deeper in their pockets. Go back to step one in my post, order the thinnest shim possible.

Note that there is a "shim club" on the forum. Do a search for "shim club" or the guy that runs it, "ghostgs1". There is a link in his signature that gives details about how the club works.

While I am pointing out signatures, check out the invitation in mine to get a spreadsheet that will help you figure out what size shims you will need. You will have to start by verifying that a stock shim can be used.

.

 

[DAVE KATO]

thanks so much Steve. your help is appreciated. tappet shims are a different animal than pushrods and rocker arms. I'll send an email.

 

[60ratrod]

2. I don't believe that an '83 GS650GT exists. There is an '83 GS650G, but the T is the letter for the '81 model year. An '83 would be a GS650GD.
.

Steve, what we here in the states know as the 650g, a lot of the world knows it as the gt. the 650 katana we know as the 650m, but the rest of the world it's the 650g, they added the t to differentiate between the 2 trim levels

 

[Steve]

OK, that's news to me. :-k

Thanks for the education.

I guess that also confirms that Texas is part of "the rest of the world". :-\\\

.

 

[DAVE KATO]

if a 2.30 is to tight(smallest I have and most kits start with this value) do the valve stems need to be dressed down, and how much would it need to be at the correct valve height?

 

[JTGS850GL]

I'm sure that others can chime in here but it would seem like you could remove the shim from the bucket and measure the gap between the cam lobe and the bucket seat. Just don't rotate the cam full circle while the shim is out. Once you have that measurement you would just need to calculate the required amount to take off by subtracting the measured gap from the desired shim size -.03mm. I would start with a desired shim size of around 2.80. Maybe 2.85.

 

[Nessism]

if a 2.30 is to tight(smallest I have and most kits start with this value) do the valve stems need to be dressed down, and how much would it need to be at the correct valve height?

The relationship is 1:1. Shorten the valve stem by .3 and the shim moves from 2.30 to 2.60. There is a limit to how much you can cut though. At some point the keepers will stick up above the valve stem so that's to be avoided, or you need to have the keepers skimmed as well.

 

[DAVE KATO]

I was hoping to not have to pull the head back off. boy fellas education is expensive. all help is appreciated. are shims available in 2.00mm?

 

[Guest]

Hi Dave, Suzuki only went down to 2.15 mm shims, I believe. In the shim club, we have a few that are less than that, polished down from much thicker sizes. If you would like to avoid pulling the valves, we might be able to help out, if we have what will work for you. Send me a pm if you would like to try. Ray

 

[JTGS850GL]

I believe that Suzuki went down to 2.15 for a reason. Much thinner then that and you risk cracking of the shim and the cam lobe catching on the shim bucket. Same thing as if there was no shim in the bucket.

 

[DAVE KATO]

gotcha. this is my first time working with the shim arrangement, but i'm startin' to snap to it thanks to all you guys. DAVE

 

[DAVE KATO]

thank you Ray, Ya think the seats were all cut the same depth? that would make life easier, right.

 

[Steve]

I believe that Suzuki went down to 2.15 for a reason. Much thinner then that and you risk cracking of the shim and the cam lobe catching on the shim bucket. Same thing as if there was no shim in the bucket.

Can't argue the cracking aspect, but the buckets are about 1.5mm deep. :-k

.