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Discussion in 'Thumpers' started by onaXR, Jan 18, 2006.
:eek1 Oh mY gOd!!!!
i have just done a dry build with a rfvc 650 bottom mated to xl600r barrel,stock piston and twin carb head.
without gaskets the piston is 1.3mm above deck height.so with double base gaskets and stock head gasket i should just about clear zero deck.
has anybody done this without issues..valve to piston clearance etc.
any advice would be great.
Acerbis made the white ones. Don't know if they're still available though.
That much piston above the top of the cylinder is not going to work.
The head gaskets are designed to be between a flat surfaces and not another gasket.
If you want to pursue make a 1.3MM solid copper cylinder base gasket.
Back in the late 70's when alcohol fuels first hit the scene, I was riding a Moto Guzzi Sport and tried two head gaskets to reduce the compression to something that the alcohol/gasoline fuel could tolerate without knocking like a forge hammer. The stack of gaskets just would not hold a seal long.
Doesn't alcohol fuel like higher compression?
If you make a 1.3 mm copper , there might be a chance that your timing chain will end up tighht. Ask me how I know...
When alcohol/ethanol fuels hit the market even my 6 cyl. Ford knocked when using these fuels.
I was relating this experience to lend creditability to my recommendation of not using two head gaskets based upon actual experience doing so.
I ran two gaskets for quite some time as I was riding my Sport daily to work.
After a rather short time the gaskets would leak and burn through.
Because of the poor reliability of two head gaskets I made a base gasket of pipe flange gasket material. It was a little thicker than two Guzzi head gaskets.
There was a reduction in performance but the bike got me where I was going till I could put lower compression pistons suitable for the newer fuels.
Here's the old Sport outside my "pad" with it's custom cover:
It was a cool bike. I had to be the first Sport Biker in Houston. Note clip on handlebars
and 10 HP worth of stickers:
Jeff suggested these in the XR600 thread when you axed the same question a week ago.
Who makes them boss
Thanks for posting the link, my enthusiasm was cut a little bit short when I found out they only make Aluminum rear sprockets but I'm still happy there is a option for custom sprockets.
plus they have that hard coat option and a option to go Xtra Lite.
Go to Fleabay and type in
99 XR600R Acerbis Frame Guards
And I bet you may find some there.
Or try Power Sport Junkie or many others for the UFO brand.
I would like some opinions from the redular gang on here.
HT,Steve and CW etc.
Regarding the camchain being 1.3mm out of place i dont think it would
have a noticeable effect.Please correct me if i am wrong.
You`d have to slot the cam gear.....as the timing will be advanced......might not hurt a thing,,but it will increase low end at the expense of top end power..
Increase the thickness of the base gasket........do not double up on the head gaskets..or a solid copper head gasket works too.
I just never saw the answer, sorry, but thanks for the info.
If the piston is 1.3mm above the top of the cylinder and you used a 1.3 mm spacer of some type at the bottom of the cylinder you would end up raising the center of the cam 1.3 mm. You would not see 1.3 mm on one side of the cam chain but .65 mm on either side. 1.3 mm split by 2 = .65 mm. The cam timing change would be negligible.
You've got it backwards. I f the cam goes up 1.3mm , that's 1.3mm per side and2.6mm total slack out of the chain. Can the tensioner give that much?
I got my slow air screw kit this week and looking at it next to a slow air screw I am puzzled as the adjustable screw needs a much larger hole. Is the slow air jet passage a stepped hole?
That`s not the only issue.like i said........
Look at it like this.......the timing chain is under under tension on the rear side...the front is basically straight up/down from gear to gear....now..if you raise the head the cam gear cannot go straight up in the front without the cam gear turning from it`s TDC marks to allow the slack.........the tensioner side will allow that because all the slack is on that side..........so if you raise the head.......all chain slack is provided by the tensioner side so cam timing will be an issue...
If the head moves up 1.5mm ...........all that chain slack comes from the tensioner side and the cam turns to provide all that 1.3mm clearance needed..
So the cam will turn that 1.3mm and you are right that 2.6mm chain slack is needed to even lift the head that much..
And you have a valid point,will it allow 2.6mm of extra chain length without issues..