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Old 07-15-2012, 03:57 AM   #16
Voltaire
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You used to be able to get a 1700 kit for aircooled VW's that were a bored out 1600.... the case end was so thin it rang when you tapped it. The experts said they failed due to cylinder wall distortion..... some did, many didn't and the BMW ones are waaaaay more substantial. thats my 5 cents worth (as due to inflation we no longer have 1 and 2 cent pieces.)
Feel free to post them up here for testing......
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Old 07-15-2012, 06:27 AM   #17
Rucksta
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yeahbut 1600 to 1700 is like 800 to 850 these are like taking a dub to 2100
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Old 07-15-2012, 11:21 AM   #18
Hawk Medicine
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Quote:
Originally Posted by mattcfish View Post
Actually Venolia's are great pistons. They are used to be very popular with racers. I had a set in my R90. They are made of a very tough aluminum alloy that has a different expansion rate than stock BMW. They tend to rattle when COLD and seal up nicely when HOT. The problem is making sure you have the proper bore to work with them. Check with Venolia to make sure. As far as the liners being too thin, I can't say.
Those have a pretty serious dome on them, could be pretty high compression.
Wirespokes reports the same thing happening with his big bore R65.

He says that the pistons slap when the bike is cold but the noins goes away oonce the engine warms up and the biks runs very well. I can't wait to ride it next month!
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Hawk Medicine screwed with this post 07-15-2012 at 07:51 PM
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Old 07-15-2012, 12:42 PM   #19
Voltaire
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Quote:
Originally Posted by Rucksta View Post
yeahbut 1600 to 1700 is like 800 to 850 these are like taking a dub to 2100
I'd like to take my VW bus to 2100....just need the new aluminium bubble case, 82mm stroker crank, 90mm cylinders......$$$$$ ....the time proven 1776 will just have to do...

As with old VW's I'm unsure of why anyone would bother with an airhead....the bang for your buck is not worth it....
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Old 07-15-2012, 01:49 PM   #20
supershaft
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Most of those sleeve's installations were not right IMO. I installed them differently. The bottom of the sleeve/cylinder does not look tight to me. The top of the sleeve/cylinder is a good indicator too but no photos.

Most pistons you will find washed like the other piston in the photos for poor bore/ring seal. That one piston is sealing remarkably well compared to the other one and most I have seen.

The problem is that those sleeves are not thick enough. Run a Sunnen hone down the bore a time or two and look at the bore. You will see corrugation of the bore right in sink with the cylinder's fins. Not good for ring seal!

I have more than a little experience with Venolia pistons. I have seen no issues with cracking. My main issue with them is that the ring grooves are often machined too wide. Ring seal is an uphill battle starting with wide ring grooves. The other thing I have noticed about them is that there is a wear pattern on the squirts that matches the machining on the inside of the skirts. I don't think it hurts anything but they do do that. The ones in the photos above haven't done that yet. They can be ordered light! Maybe some are ordering them a bit too light?

supershaft screwed with this post 07-15-2012 at 02:00 PM
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Old 07-15-2012, 07:04 PM   #21
igormortis
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So, are these problems inherent due to the liners being iron? Could it be solved by boring another pair of ’80 cylinders to spec, and having them re-nikasil’d?
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Old 07-15-2012, 08:04 PM   #22
supershaft
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I can't remember if those liners are iron or steel. I would hope iron but . . . . Aluminum is a lot more thermodynamic than iron or steel. I would think the problem would be worse but I don't know for sure. Some suspect the nikisil big bore kits are bigger allowing a thicker cylinder wall but I don't know. That wouldn't change the cylinder being damn thin alongside all the stud bores. They don't look bigger but 2mm all the around might be hard to notice? I wouldn't think so but . . . .
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