880cc, where can one buy one?

I have bored a lot of barrels for 79mm pistons. About one out of five has ended up cracking the spigot that fits into the case when sleeves were not installed. I have also seen porosity that caused leaks between the fins after they were bored without sleeves.

I generally recommend sleeves for 79mm or larger.

I have had very good results installing thick walled sleeves and boring as large as 80.5mm. That seems to be the limit for long term reliability. Jim

over here in belgium the 920 conversion was generally used on scramble outfits
we used a few of those engines (as base ) on our roadracing outfit but were no faster than our later 850 std bore engine ( a nourish crank gave no advantage either )
the 920 was quicker out of the turns but lost out on the staights , not willing to rev higher.the pistons were cosworth with theit skirts turned of , something like slippers
compession was from 9 to 1 up to 11 to 1,by shaving of the head and putting steel shim-gaskets under the barrel to experiment
remember these engines were put together with tlc and a lot of patience , not std ,

the 920 left not a lot of meat on the barells , one could see the liners behind the pushrodtunnels at the bottom of the barell

i wouls say that a 920 is not a good idea for a roadbike but a lot of fun for playing silly buggers with , but be prepared to pay the price in time and money

I think TC Christenson sold them and still may.

comnoz said:

I have bored a lot of barrels for 79mm pistons. About one out of five has ended up cracking the spigot that fits into the case when sleeves were not installed. I have also seen porosity that caused leaks between the fins after they were bored without sleeves.

I generally recommend sleeves for 79mm or larger.

I have had very good results installing thick walled sleeves and boring as large as 80.5mm. That seems to be the limit for long term reliability. Jim

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I think Jim's got the right idea for reliability on the street. I've had really good luck with both iron cylinders and aluminum cylinders sleeved for 91 mm bore, but that's been mostly on race bikes. I'm not sure of their longevity on the street. I ran one in a street bike for a while, but didn't really put a lot of miles on it. I've also been lucky with boring cylinders to 79.5 mm, and have one in a street bike right now, but it's always a risk, and if I ever do another one I'll probably sleeve it first.

Ken

With safety in mind, at what displacement should one say goodbye to the standard gearbox and hello TTI?

Glen

worntorn said:

With safety in mind, at what displacement should one say goodbye to the standard gearbox and hello TTI?

Glen

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That more up the the rider and it's use than the displacement.

My bike makes mid 70's for horsepower. If I were to hammer it in the bottom two gears I would undoubtedly break it. But with care I have ridden for years with a stock box.

A tuned 750 will easily break the gearbox if you are trying to roadrace. I broke many of them. Jim