Relieving the exhaust port bridge - a 41 year old mystery SOLVED?

[racerclam]

where is your sense of adventure

Rich

[viclioce]

The bike was used. If a dealer couldn't have a bike for sale ready to ride, why would I consider it? I was 18 at the time!

[viclioce]

Max, or someone. Can you point me to the published "How To" for doing this? I don't want to damage another cylinder and would like to have something published I can read and follow. Is it stored on the forum somewhere? Or in a back issue of the Resinator? Please let me know. I'm off to find a stone today. Would like to read the publication and have it handy. I also need to find feeler gauge with .003 gauge in it. What's a good location to try to find one? I have an AutoZone & O'Rileys close by to my house. ; D Victor

[hodakamax]

Victor, there's a service bulletin part of which I posted on page one. There's also a picture of the type of stone you're looking for. I got mine in the fishing tackle department. Be careful out there!

Max

PS--I did the clearance measuring by pushing a ring (using a piston to keep it square) to the center of the bridge and measuring it with a feeler gauge.

[Bullfrog]

Um, place rounded end of whetstone on exhaust bridge. Rub stone back and forth. Check progress. Repeat as needed.
Ed

[viclioce]

Yeah, Ed. Nice technical info. Thanks. ; D Victor

[Bullfrog]

That's how technical the job is. Do it all in a craftsmanlike manner and you'll be good to go.
Ed

[viclioce]

Well I got a good .001-.020 feeler gauge today. Man. Talking about removing material no thicker than a sheet of aluminum foil! This should be Interesting now that I have a gauge! ; D Victor

[Bullfrog]

OK. Yup, you are not removing much material. Just to clarify - in my previous technical advice post, the phrase "back and forth" means to rub the stone on the bridge with movements in the same directions the piston moves (parallel to the center-line of the bore, not sideways across the face of the bridge).
Ed

[DGardner]

This is what a exhaust port bridge should look like after you use a stone to relieve the bridge

This is what a piston looks like that has started to stick.

This is what I do with every bike I have that has a bridge. Put the piston on the rod without the rings, put the cylinder on and mark the bridge outline on the piston and then drill two small oiling holes in the piston.

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images (1).jpg (4.83 KiB) Viewed 5987 times

This should help from sticking a piston on the bridge again.

[admin]

Very nice Doug!

[spudman]

I like the idea of the "cooling holes" Doug! For some reason though, I'm able to click on and enlarge the first two images in your post, but not the bottom two. I tried different browsers and nothing seems to work. I'm just trying to get a better view of the image with the two yellow arrows so I can read the text (hole size?) to the left of them. Thanks!

[dcooke007]

Spudman,
Doug cant respond at the moment...at work. Said to relay to you 1/16th inch.

Danny Cooke

[spudman]

Thank you Danny. When Doug has time to respond, maybe he can give us an idea of how far down from the top or up from the bottom the holes are drilled as well. Also, can we safely assume that there is no weakening of the piston that would occur here with the two small holes? I would think not, but just wanted to be sure.

[dirtsquirt80]

would you still drill these holes if you had a savage port?

[Bullfrog]

? ". . . savage port"? I don't know what that is.

Ed

[DGardner]

Thank you Danny. When Doug has time to respond, maybe he can give us an idea of how far down from the top or up from the bottom the holes are drilled as well. Also, can we safely assume that there is no weakening of the piston that would occur here with the two small holes? I would think not, but just wanted to be sure.

I would put the first hole about 1/2 to 3/4 of a inch from the top of the piston and the next one about 1/2 from the first hole. I've never seen a problem putting holes in the piston.

[DGardner]

The only problem I have ever seen with putting the oiling holes in a piston was the time a friend thought he could judge the center of the piston! He put the cylinder on and when we looked in the exhaust port and there was two small holes right next to the bridge.
Like Maxwell smart on the get smart TV show would say "missed it by that much"

[spudman]

Thanks for the info Doug!