Project Fuel Injected Turbo FZR250, half

Little project that I've been working on for about 20 years now. In the middle of a rebuild after it dropped both exhaust valves in one cylinder.
Engine is cylinders 3&4 only. 1&2 have been cut off and the end of the block and head blanked off. Originally ran an Ecotrons engine management system kit for a GPz250. The twin throttle body plugs straight in. The kits are very reasonably priced and after a bit of fiddling it was up and running.
Due to suspected problems with the system I upgraded to a Link Atom engine management system. The turbocharger is an IHI RHB31A. The motor pulls boost from about 10000rpm. Best power to date was 32rwhp.
One interesting part of this project has been finding all the differences between the original 2KR base motor and the new motor based on a 3LN

 

You've got to be introduced to @gregt - also from your side of the pond and it seems imbued with the same sense of ingenuity

Is is something in the water over there?

WHOOPS, where are my manners

Welcome

 

I've met Greg. Collected a couple of unused spare 3LN motors just before Christmas for my rebuild

 

Another saw handy motorcycle enthusiast , well done .
How's the balance now ?
Some build pics would be nice

 

Hi, do you have a video on youtube of the 2 cylinder by any chance? I seem to recall seeing one.

 

welcome.

 

Is this yours?

 

This one is with it fuel injected using the Ecotrons system but no turbo:

 

The balance seems fine. Basically it is a 180degree twin. I've ridden it a few times and thought it was fine.

The build has been documented on Kiwibiker starting about here: https://www.kiwibiker.co.nz/forums/showthread.php/68694-6/page51.

The bike, #6, has had a couple of engines over time. Prior to the FZR engine I had Honda MB100 engines in it

 

I'm a bunch of pages into the kiwibiker thread - <DARTH VADER MODE> HMM, Impressive! </DARTH VADER MODE>

 

I also enjoy cutting tools & speed

 

I like it

 

I cut the new cylinder head using my drop saw with a new 60T blade. Nervous to start with but it went through it like it was made for it. Made nice chips and everything. I love these little 250 Yamaha engines. Considering the abuse and lack of maintenance inflicted on them they seem to do OK. Pistons and bores have practically no wear. There is often a scorched bearing on the crank somewhere but the crank bearing surface has been good so far. The heads suffer a bit but I think that's down to the shops not wanting to work on them and riders simply not doing maintenance, valve clearances tighten up and valves and seats get overheated due to leakage. Every head I have looked at has had bad problems with valve sealing and often a dropped valve though I'm not sure what has been causing that. One possibility is the lack of spring pressure. Every spring I have checked is not at the correct installed height.