Need help with this cylinder

BombThreat

BombThreat

'Diggity
Location
Johnstown, NY
I just had a diffrent thread about this cylinder http://www.x-h2o.com/threads/14623

**I need you help guys, I bought this cylinder thinking it had a few bores left on it. Turns out it doesn't. Also let me say I'm still learning as we go here, so be pacient please.

Q#1) The Inner cylinder is right about 85.5MM and the bottom outside is 90MM Does this tell you its a stock sleeve or a 760 sleeve has been installed?

Q#2) If it is infact a 760 sleeve, would it been worth my time/money to have it resleeved or just find a stock 61x cylinder in nice shape? Im not trying to go crazy with this boat, just want a nice 701 in it...

Thanks for the help!

****PICTURES****
http://www.bombthreat.net/ski/61x001.jpg -Top

http://www.bombthreat.net/ski/61x002.jpg -Top

http://www.bombthreat.net/ski/61x003.jpg -Bottom

http://www.bombthreat.net/ski/61x004.jpg -Weld

http://www.bombthreat.net/ski/61x005.jpg -Mysterious stuff on wall...
 
Last edited:
meatball

meatball

User Title Unavailable
Location
Maryland
sleeves come in all different sizes. First off, what is the cylinder is it 61X? Look at the stamp in the middle of the side (on one side) of the cylinder. I'd say, rather then just spend more money, just run it like that. With a new bore you have to get new pistons anyways, why not make the best of what you got? Post up some pics, it may just be regular sleeves bored out, or beefier sleeves may have been installed.

I say run it the way it is, then when the topend goes after 400 or so hours, replace the sleeves (if you dont want to go out to 86mm)

Not really a huge difference in 701->760 when the only variable is displacement. While it does make a difference, its minimal IMO.
 
meatball

meatball

User Title Unavailable
Location
Maryland
I'm not expert enough to tell if those are beefier sleeves, I'm sure someone else here is, but I'd just run it as is. Get some 85.5 mm pistons, give those to a machine shop and have the clearance and hone the cylinder if needed. Run it like is, if the bores still good, why waste all those possible hours and 'skip' the bore its on?
 
BombThreat

BombThreat

'Diggity
Location
Johnstown, NY
Well, Im worried that if I spend all this time and money building this engine that it may explode mid-summer and kill everything... How likely does that seem? Also Ive got a few more pictures coming..
 
meatball

meatball

User Title Unavailable
Location
Maryland
why would it explode because its on an 85.5 mm bore? I dont have personal experience in this, but I hear its safe to run to 86mm. Running a bigger bore doesnt decrease life expectancy, and what Im recommending will save you money, verse resleeving it and 'skipping' the bore its on currently.

The most likely causes in engines grenading, is number one: ring snags, and number two: crank bearings. Everything past that is miscellaneous, like a screw coming off the reed cage or something.

I've only lost one engine so far, it was a crank bearing.
 
Boris

Boris

The Good Old Days
Location
The surf-less coast
That "mysterious stuff on wall" is piston matter.
That happened when the rings got snagged on the exhaust port and she done blewed up.

That's a nice size chunk missing from the sleeve.:bigeyes:

Not only is that cylinder welded but it also has a bite taking out of the sleeve. If it was me I would scrap that thing and start fresh.
 
Boris

Boris

The Good Old Days
Location
The surf-less coast
That stuff stuck to the wall is aluminum from the piston that rubbed itself onto the cylinder wall. That can be cleaned off.

If you look at the top of the port there is a visible portion of the sleeve missing. That's the chunk I was talking about.
 
meatball

meatball

User Title Unavailable
Location
Maryland
I dunno, those pics are looking pretty sketchy. Now I see why you were questioning whether or not to run it. When a piston snags a ring all the friction heats it up a lot. I wouldnt doubt thats part of the previous piston.

Really thats porting? I've never seen anything like that. Got pics of the other cyl hole?
 
kurtwolff

kurtwolff

Location
Mooresville, NC
So I take it that the trade we had agreed on is no longer valid? Also would have been nice to mention that weird a$$ porting and the piston melt toward the top of the cylinder.... I have your stuff boxed up, let me know what you want to do. Thanks -Kurt
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
I have seen that type of porting before.
I think it provides a little bit of blowdown before the rest of the port opens. Not sure why.
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
If you going to use it for freestyle, IMO i don't think it will work very well. The notch in the top of exhaust port was done for race motors with a lot of compression ratio and helped motors to start (we used KV ignitions and lame msd's, back then) as we didn't have the MSD programming for start-up features that we have now with the new digital MSD boxes.
 
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