I had two close realtives who are accomplished machinists and experts in auto and bike drag race engine building both tell me to heat the heads to about 210 degrees F to remove or install guides.
As an experiment, I removed an exhaust guide from a damaged but repairable head without heating. Then I removed and replaced an exhaust guide in another head using the preheat (and new guide in the freezer) trick. I could not tell a bit of difference in the two removals.
If you do it yourself, make sure to remove all carbon from the old guide before drifting it out as the carbon can slightly ream the hole as the guide is forced back through it. Also get a mandrel suited for driving guides in to minimize distortion of the guide (which results in more reaming). DAMHIK. Mandrels are cheap enough. Its the reamers that hurt the wallet.
__________________
Merritt Island, FL
95 M900 -- Running again!
92 900SS Basket Case -- Now a track bike
99 BMW F 650. Old Reliable
83 BMW R80 ST-- Airheads are cool!
|