Valve guides

[blade625]

I pulled my heads to clean them up and lap the valves [I am not too bright. I raced this bike for two seasons on 110 race gas, and never fogged the motor after the weekends, resulting in a fair bit of corrosion]

anyhow, I decided to check the guides with a bore guage. Everything checked out except for the H cyl. exhaust guide. Max clearance is spec'd at .00314
The guide seems to have a bit of taper. At the rocker end I have .0012 [well within spec.] but at the seat end I have .005 which is well out.

My questions:

1]Is this guide considered toast?

2]If I replace this guide, do I really have to heat the head to 365deg to drift it out? And then heat it again, and freeze the new guide in dry ice prior to driving it in? [my, thus far, very tolerant wife is going to love me being in the kitchen, cooking motorcyle parts in the same oven that she puts roasts and turkeys in....]

3]can you get guides that are bored to the correct size? or do you have to bore them out yourself? valve stem right now is 7.97mm [.314] and looks fine.

4]Is this something that is generally better left to a machine shop that does head work?

[chaas67]

I don't have anything worthwhile to add but, I'll take a guess that if the wife doesn't go for #2 then #4 will be the safest option...

As mentioned here before, 'Do whatever the f@$% you want is not a Yes'

[blade625]

Originally Posted by chaas67

I don't have anything worthwhile to add but, I'll take a guess that if the wife doesn't go for #2 then #4 will be the safest option...

As mentioned here before, 'Do whatever the f@$% you want is not a Yes'

Hey, if she goes for #2....then it opens the door to start powdercoating little bits and pieces [isn't baking them part of the process?]

[robtg]

Judging by questions 1 through 4, take it to a pro that has a proper machine shop and will set it up right. ---RG

[mark1305]

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.

[SP544]

You should definately replace that guide. I would say if you feel comfortable doing such work yourself then go ahead and give it a try. I do a lot of my own work and recently rebuilt the upper end, but had the guides replaced by an expert to give me some peace of mind. Your local Duc dealer should have a machine shop they can recommend for that work if they don't do it in house. Good luck.

[NC Rick]

I have replaced guide in an aluminum head on a car and on a BMW twin. All I used was a punch that I sized on a lathe and in the car I used an air hammer to push them out and in (warmed the head). On the BMW I used a press. In both cases, I reamed the guide after and then touched up the seats with a nu-way cutter. The car lasted us for 170,000 miles and the Bike got sold about 50,000 miles later (my friend Vann’s bike). Another friend needed guides in his Moto-Guzzi and sent out the heads to a shop that only did heads. It ran for a few miles but the guide came loose and it was not concentric so the valve stopped seating and burned. I think what I am saying is do-it-yourself or send it to someone who really knows the heads and what they are doing.

[gixracer]

ds heads have a service bullitin out now

the guides are oversized check with your dealer.
also the correct size guides are not avail and are on backorder

[blade625]

Originally Posted by gixracer

ds heads have a service bullitin out now

the guides are oversized check with your dealer.
also the correct size guides are not avail and are on backorder

Yeah, Leslie at BCM already hit me with that one [re: the troublesome 1000 guides]. I should have been more specific in my original post, these are 750 heads.

anyhow, no point in me mucking about on a set of heads that were actually ported by Bruce. no point in risking screwing up his very nice work.

these babys will get shipped to a pro.

thanks to all who provided input