What are your options when a bike has high k's?

[Coyote]

I was wondering what can you do to fresh up a high mileage bike? I've heard of engine reconditioning, honing cylinders, reboring, oversized pistons, etc. but don't really know much more. How easy is it to get hold of oversized pistons? Are there generic pistons that you can get in the size you want or does everything have to be made specifically for the bike? How much can you bore out a cylinder out by before getting too close to the coolant channels and other cylinders?

Mainly thinking of my VFR in the future, and if I was to buy a classic such as this: http://www.trademe.co.nz/Trade-Me-Mo...-190508002.htm

However and general info would be appreciated.

[Ixion]

Firstly, of course, the question is "how high is high". For some bikes 100000km is just run in, for others it's scrap heap time

But a generic response to your questions:

In most cases (plated bores are an exception) the part that wears the most in an engine is the cylinder bore/piston/rings . As you mention, the cylinder can be overbored (just a bigger hole bored in it) and larger (oversize) pistons fitted. Pistons are more or less specific to each bike, ie you need VFR pistons. Normally they come in two oversizes, +20 and +40 (thou) . A few have a +10, a few have a +60. And there are odd ball others. You buy pistons oversize enough that when an engineer bores a bigger hole the bore will be nice and circular again.

However, once a four stroke engine has worn sufficently to make a rebore necessary, one must look with great suspicion at other wearing parts. They may not be as obvious as the bores, but they wear too, and a nice new rebore won't be much use if the big ends go. So you need to think about the crankshaft and bearings (main and big end): plain journal cranks can have the journals ground and oversize bearings fitted (oh all right, technically they'r undersize). The vlalve gear will wear, both the valves themselves, and (notoriously on some Jap bikes) the cam journals. These can't usually be remachined you have to replace them

Then there's the clutch , and the gearbox. Just to be going along with. Oh, and the oil and water pumps. Don't forget the oil pump.

It varies from bike to bike.

Of course, if you have a two stroke everything is SO much simpler.

Oh, getting the parts for a recondition varies from "Go to dealer, order stuff pay (lots of) money" to "search Ebay for years, pay mega dollars for something that's been sitting on a shelf for so many years that it's now unusablke when you finally get it " to "make it yourself. You don't need two kidneys"

[Coyote]

Firstly, of course, the question is "how high is high". For some bikes 100000km is just run in, for others it's scrap heap time

But a generic response to your questions:
...

Would that CBX have been 'run in' by now?

I might put the effort into my 400 in the future if I still have it. But I think my thought of freshing up an cheap, old bike for commuting on might be a touch unrealistic.

My 400 has a complicated engine. It's got cam gears that must be wearing thin. Might save all this effort for a grander bike, like an RC30.


On a tangent, that 500cc twin cylinder 2 stroke that was posted up lately, that's got my interest. My brother is entering a fabrication course next year at Weltec. Hopefully with his skills we might be able to make our own bikes around that engine. I've also thought of putting 2 of them in a Mini Clubman

[racerhead]

If its any help Ive heard of a couple of 400 v4's with over 80,000km's on them
and their still going strong. If the engine is well looked after it will last the distance but the things to look out for are all the suspension pivots, headstock bearings and all the other bearing surfaces on the bike which will wear out.
Also getting oversized pistons for the vfr/rvf is pretty difficult as they cant be got off honda.

[bsasuper]

Generally motorcycle parts are expensive, even if you assemble it yourself, if anything needs machining its expensive, older model bikes will have pattern parts to choose from but anything about 10yrs old will still cost a bundle, of course im talking about big sports bikes.

[Taz]

My BMW has 120,000 kms and sill runs like new. I doubt that the ducati would go that long without rebuilds.

[lostinflyz]

ive got an nc21 with 96 thousand on it. goes great. parts wear and there are a few fatigue failure pieces about but nothing major. gear box is only now starting to go but thats from me being rough on it. but overall its great.

ive got a few dimantled vfr engines and have alot parts from them lying about. outside the bearings -which arent too bad all the gears (both box and cam gears) look in good nick from 2 different motors-both of which have seen long k's and had a thrash. the cranks dont look to flash and would need a bit of work to be nice agian

if it needs new parts outside pistons and rings - your often best to source a buggered motor and use second hand parts - makes life quite cheap in the end.

[The Pastor]

my cbr250 has 70 000ks. in about 30 000 she'll be just run in

[Hitcher]

My 2005 FJR1300T has just ticked over 80,000km. It has never run better.

[riffer]

My 2005 FJR1300T has just ticked over 80,000km. It has never run better.

Yes but every time you drag it out of the gargre you put a couple of thousand kms on it.

[Hitcher]

Yes but every time you drag it out of the gargre you put a couple of thousand kms on it.

I've only owned it since the end of July 2006. Mr Yamaha NZ only managed to get 4,500km on it as a demonstrator.

[AllanB]

I've only owned it since the end of July 2006. Mr Yamaha NZ only managed to get 4,500km on it as a demonstrator.

Now this is interesting as it brings to mind the whole - 'how do I run-in my new engine?' thread(s) - lets face it demo bikes tend to get run-in on the 'quick' side and its good to know than 80,000 later the beast is still running strong. I know a couple of people who have purchased ex demo rides and all have ended up running high fault-free kms.

Mind you I suspect it has not actually cooled down since purchase!

And its not a Suzuki........

[Corse1]

My BMW has 120,000 kms and sill runs like new. I doubt that the ducati would go that long without rebuilds.

Spoke to a guy racing his ST2 in bears. Takes all the fairings off and goes hard. Puts the fairings back on for the road. He had the bike since new and at 100,000km,s decided to freshen the motor for no good reason other than the mileage. He could still se the hone marks in the bores but chucked a set of rings in while he had it apart. He said he should not have bothered...............