Can any machine shop bore out a 787 cylinder to the next size (0.5)

[eyecatcher201]

Thought I have a good pair of cylinders, but the machine shop though there was minor wear and it would be best to bore cylinder out to 0.5 and purchase new 0.05 oversize pistons. Question: Is there a special procedures to bore out a 787 jug? Can any good machine shop do this and what is the average price (LI NY)
I understand that when you go much larger you have to take some off the rave valve.

 

[griz400]

I bored my cylinders to 82.75 mm bore can bore to 83.50 is the max, but have a machine shop check them, and make a bore first to see what size pistons you need, by reading your post i guess they have, i live in tampa, mine cost 85.00 and they were already bored to 82.25, u can get pistons in .25 mm increments to 83.50. have themtell you what size,take them the pistons for the final bore and hone -- word of advice, most good machine shops are at least 2-3 days behind ok , lol, you hate to hear that if u needs cylinders fast, mine is a 1999 gtx rfi, but you havent listed your year

also, post problems with your ski in 2 stroke pwc forum, ok ???

 

[Seadoobuddy]

Hi Guys,
I've heard the the cylinders need to be tapered at the bottom, and that regular machine shops MAY NOT know this.

Is this true?????????

 

[BMANN06]

What I did was print the section of the manual that covers the cylinders and took it to a machine shop. This saves them from having to dig up the tolerances of yet another engine.

SDB:

There is a tolerance for taper in the 4 tec (130/155). It is between 1/1000th and 4/1000ths of an inch. To OP these are not the taper tolerances for your 787 cylinders. The tolerances on the 787 are wait just checked the manual ... and they are the same.

 

[griz400]

Thought I have a good pair of cylinders, but the machine shop though there was minor wear and it would be best to bore cylinder out to 0.5 and purchase new 0.05 oversize pistons. Question: Is there a special procedures to bore out a 787 jug? Can any good machine shop do this and what is the average price (LI NY)
I understand that when you go much larger you have to take some off the rave valve.

i see u bumped a thread about your rave valves, i would have posted on it, nut its one of threads that was for info only, --- well, anyways, your raves can be easily done by yourself, its real simple, i did mine in like 10 minutes each, first determine what u need to take off, then scribe a line on your rave valve, (for amount to take off), actually, the metal is very easy to file right off, i used a mac half moon course metal file, then a sanding jig, (has sand paper in a flapper wheel), i put in my diegrinder, and it smoothed it right out and actually put a super smooth (polish) like surface on it -- dont be scared, i actually took off like .020 off when i should have taked like .015, didnt matter one bit performance wise, a little more is good, not enough and your piston will kiss it -- heres a pic of a flapper wheel like i was talkin about, i used a little different one (smaller) than this, but it works -- http://www.harborfreight.com/catalogsearch/result?q=flapper+wheel -- heres the file, yellow handles, all the way too right -- mine little more expesive == http://www.harborfreight.com/5-piece-12-inch-file-set-7520.html -- but this will work fine

forgot to say, i put shop rag on valve and gently clamped in vise,makes it easy to measure, scribe, file and sand

 

[Seadoobuddy]

i see u bumped a thread about your rave valves, i would have posted on it, nut its one of threads that was for info only, --- well, anyways, your raves can be easily done by yourself, its real simple, i did mine in like 10 minutes each, first determine what u need to take off, then scribe a line on your rave valve, (for amount to take off), actually, the metal is very easy to file right off, i used a mac half moon course metal file, then a sanding jig, (has sand paper in a flapper wheel), i put in my diegrinder, and it smoothed it right out and actually put a super smooth (polish) like surface on it -- dont be scared, i actually took off like .020 off when i should have taked like .015, didnt matter one bit performance wise, a little more is good, not enough and your piston will kiss it -- heres a pic of a flapper wheel like i was talkin about, i used a little different one (smaller) than this, but it works -- http://www.harborfreight.com/catalogsearch/result?q=flapper+wheel -- heres the file, yellow handles, all the way too right -- mine little more expesive == http://www.harborfreight.com/5-piece-12-inch-file-set-7520.html -- but this will work fine

forgot to say, i put shop rag on valve and gently clamped in vise,makes it easy to measure, scribe, file and sand

Griz - What do you use to measure the .015 that needs to be filed off, to make the scribe?

 

[griz400]

2 feeler guages and a scribe 1 as a guide, 1 staked on top of it what u need to take off and scribe on it -- not real technical

 

[LouDoo]

This is not my idea, I got it from SeaDooSnipe, use the new piston as a guide to shape the Rave valves.

Lou

 

[Dr Honda]

Any shop can cut it... but a good shop will want the new pistons first, and they will need to know the tolerance for those pistons. I won't cut a jug unless I have the piston to measure.

 

[Spimothy Leary]

Any shop can cut it... but a good shop will want the new pistons first, and they will need to know the tolerance for those pistons. I won't cut a jug unless I have the piston to measure.

exactly,
you definitely want to dig up the right shop, not just any shop, what I did locally was to contact about 5 buddies that have done a ton of rebuilding and 3 of them recommended the same shop
some old geezer that knows his stuff, now 4 of us recommend him.