Topic: Slotted Sleeves for Big Bore kits, why?

[aggiepike]

Back story of this which may help.

bought the bike from a friend knowing it had a motor issue. took it in to the shop and it had been bored to 67mm for 895 kit but had broken piston sleeve. So I decided to go w/ an 836 65mm, not the 895 67mm. Bought the new pistons and cylinder block took it to the shop to have them get the block bored and put it all back together. This was back in early February.

Fast forward to today. I thought I was going to finally get my bike back w/in the next day or so until about 3 hours ago. I got a call from the shop and they said they have a problem with the rods. this bike has some old MTC aluminum rods in it that are much bigger than stock obviously. Up to this point they said these wouldn't be an issue. So I go up there and they tell me that the rods are bumping the piston sleeve because it is not notched like the previous one block that housed the 895 kit. Now you would figure they would have seen that and thought about it but didn't. Now they have to send it back out to get the sleeves notched.

Needless to say I am not to happy w/ these guys but not much I can do at this point besides wait some more.

What I would like to know is can anyone tell me if slotting the sleeves was/is required on these really large big bores. Or does this mean it has some kind of stroker crank in it also? The shop didn't split the case and don't know, (which blows my mind but that's another story) and are guessing like I am. I figured someone around here would be able to shed some light on it for me. As always any info is much appreciated.

Here's some pics for you to see what I'm talking about.

thanks,
richard

[Retro Rocket]

Hmmm, i know the MTC rods are quite big in size, maybe thats why the sleeves are relieved..?  I wouldn't slot the sleeves like that again, the sharp square corners are going to help them crack, {which is probably what happened},  they should be rounded off in the corners to help avoid them doing the same thing again..... 67mm is 888cc......

[aggiepike]

Here's a picture of the rod w/ new pistons attached if it helps.

Maybe I'm wrong on the 67mm then. Is 67.5mm an 895 then? I remember looking it up when I had them measured and it was 895 but oh well now. Thanks for the heads up though gotta get my lingo right. 

thanks for the advice on the sleeve. I'm not having it notched the shop is having it done. Do you think a machine shop would know better than doing is squared like that again or should I request that they do it that way?

thanks,
richard

[Retro Rocket]

I don't expect anyone to know anything, i tell them exactly what i want, that way i know i'll get things done right....

A lot of 67mm piston kits were sold as 900 kits, they are actually 888cc, 67.5mm is 915cc...

[MRieck]

The rods are the problem....not the bore. If somebody "slots" them I'd use a ball...not an end mill. That is a lot of slot cut into those originals....why did that sleeve break?

[aggiepike]

Got it Retro thanks I'll let them know.

MRieck not sure why it broke?

So the rod being so wide is the problem issue and nothing else?

[Retro Rocket]

MRieck not sure why it broke?

I would say it broke for the reason i pointed out earlier, its the same reason polishing internal engine parts makes them stronger, any sharp pieces or sharp edges are more prone to breakage {cracks}  than smooth rounded parts....  I may be wrong about that sleeve but its definitely a possibility....

[bear]

We run "Stroker Cranks" in our motors and have no need to notch the sleeves.

Cheers,
Brian

[754]

 Steel rods are slimmer, and need less clearance..

[Big Jay]

If I remember correctly, 68 mm was the point where the aluminum rod would hit the sleeves. Anything smaller required the sleeves to be notched.

[sohc boy]

those MTC rods are thick allright ,used them till one let fly,an yea need sleeve notching on small bore , but as retro rocket says , i wouldnt notch like that ,seems bit too  much of a cut out anyway, gota check length of sleeve also where sleeve pokes out barrel ,

[aggiepike]

Thanks for all the info and advice guys. Since this is all new to me need a little more advice on how to tell them what I need and expect. Do I tell them I need this notched w/ rounded notches and not hard 45's? Don't know the lingo for this if there is even one, I  just want this to explode after all the hard work and $$ that has been put into it.

Richard

[754]

 It is a notch actually not a slot.. just make sure you have about 60 thou clearance..

 You should see the scary nothing on big bore  STROKER V-twins sleeves AND PISTONS... looks frightening..

 That broken Aluminum riod looks waaaayyyyy better than the Yosi  rod bits I pulled out of a1080- KO lower end I bought.. it actually imprinted the rod bolt into the crank...

[sohc boy]

...Aggiepike ,those rods used or new ,if used ,i'd think twice about using them ,been told they have a use by date , as you said , you dont want it to explode after all you hard work