YZF426 another bloody Yamaha

[pecrazy]

Had this YZF426 for a few years, bought it in pieces with cracked cases around the kick starter. Must be a really low hour bike as it's on it's second rear tyre and original chain and sprockets. I 2 packed the frame, cleaned a heap of parts, ordered second hand cases and a heap of new parts then it sat for almost 3 years as Yamaha's are not at the top of my list as has been reafirmed with that IT200.  Came with a spares kit with gaskets and new rings, I put in a new piston, timing chain and cleaned up the valves, everything else was as new.

[FourstrokeForever]

Looks as good as new!

They are a rocket ship of a motor.....Aside from the don't let it kick back or you will break the cases, as long as you keep a very close eye on valve clearances they can be reliable. Once valve clearances are let past tolerance, they are a literal hand grenade. 

[pecrazy]

Valve clearances were on the higher end of clearance, guessing they would get tighter with wear so should be good.  Probably won't ride it much anyway. Only missing one dowel pin and a couple 6mm bolts so far, just gotta rat through the stuff to find everything.

[LWC82PE]

as long as you keep a very close eye on valve clearances they can be reliable. Once valve clearances are let past tolerance, they are a literal hand grenade. 

+1 very important i agree, because when they drop a valve its not pretty and you can kiss goodbye your whole engine.

[Nathan S]

They're damn solid compared to most of the 450 that came after it. Second rear tyre would be way beyond the reliable life span of some of the 250Fs...

From memory, the 400/426 cranks become an issue after a lot of hours, and so do gearboxes - but it is more of an issue for the WRFs than the YZFs.

Looks like a decent old unit.

[sleepy]

Probably a bit late as you already the motor together but I would have recomended a new set of valves if it has the original Ti valves are still in it. The early titanium valve had a habbit of dropping of the head and if you went anywhere near the seating face with lapping paste you will be changing shims after every ride.
 

[b490]

[sleepy]

I've repaired quite a few that looked like that. Take out the seats, weld up the damage then re-fit seats. Mostly need to replace broken guides as well. A lot of work but generally cheaper than a new head.

[pecrazy]

Really looks to have had an easy life, tyres worn square not rounded off at all. Sprockets not looking like a saw blade so all indicates he wasn't a throttle jockey.  Budget build as usual and more than likely never get ridden in anger.

[sleepy]

You should be ok then.
When the 250F Suzuki's came out the service book said to replace the valve every 20 hour but some didn't even get that long.

[tony27]

You should be ok then.
When the 250F Suzuki's came out the service book said to replace the valve every 20 hour but some didn't even get that long.

You mean the kawazuki 250, I remember the jokes about if you were really quiet you could hear the ticking in the showroom. I was shocked when I first heard that the spares kits included a piston kit with shorter recommended replacement times than for the 2 strokes
Is the 426 the 4 speed motor or was that the first 450?
Looks really tidy & well looked after

[sleepy]

They were the same motor at the start.

[pecrazy]

5 speed I hope, gearbox was in a ice cream container when I got it.