FXR150 conrods breaking

**Sideways Sam** · 5th January 2009, 10:40

Originally Posted by dangerous

Yeah thats what I was thinking, same damage when my CB droped two valves.

forged, carillo... yeah right these engines are a malaisain run about only that spilled over to NZ, china parts only.

There is another option....... I didn't recheck the valve piston clearance after adjusting the valve timing which moved by about 8 degrees. Theoretically that could do it, allthough it's unlikely in my book.

I've never heard of an FXR dropping valves, all the retainers are still in place and there are no broken springs.... I was running the factory CDI so the rev limiter was still in operation which should eliminate valve bounce......

**TZ350** · 5th January 2009, 12:12

Did you change the cams? Extra lift? With the changes to the head and barrel, could the valves have been getting caught on the outer edges of the valve pockets cut/cast into the piston crown? 8 degrees, could the valves have come together and hung up long enough for the piston to hit them?

**cmac** · 5th January 2009, 12:26

Originally Posted by Sideways Sam

OK,

I had thought she might be fixable but now I think I can trash just about the whole lot........

Here we go:

* - Shrapnel found everywhere, carb, exhaust etc

* - First sign was when I removed the plug which had the end completely destroyed

* - Crankcase smashed to pieces, originally I thought it was just the hole throught where the rod penetrated just behind the barrel but it has destroyed just about everything including smashing a large chunk off the front of the case

* - Barrel destroyed including crack right up one side and skirt totally missing (I found most of the skirt in the exhaust pipe)

* - Head cavity completely munted including 3 missing valve heads etc

* - Almost nothing left of the piston, most of it seems to be floating around inside the crankcase

* - Crank is a bit of a mess so probably won't be any good either

My guess is that the piston and valves came into contact, I don't know whether this happened before the piston lost it's conection with the crank or if the broken rod was a result of the piston hitting the valves.

Interestingly the rod broke at the top, unlike the other's I've seen which have broken at the bottom. By breaking at the top it could go up and down inside the barrel ramming the piston into the valves/head repeatedly which has obviously happened in this case.

Still don't know which comes first, the chicken or the egg..........

Has anybody ever thought about whether the coolong is adequate on these things? anybody run a temp guage?????? If they were getting too hot that could explain all manner of problems. Running too lean could cause similar issues, I think that may have been my problem.

I dropped a valve on a Triumph once (at about 80mph on a gravel road

) and the head looked just like this one. The difference was the piston didn't break - the valve ended up welded into the piston!
IMHO I reckon the piston/conrod have been intact with a loose valve head floating around the bore for quite a few revs - though I do acknowledge your comment about the stems/springs etc being intact.

**Sideways Sam** · 5th January 2009, 16:44

Originally Posted by TZ350

Did you change the cams? Extra lift? With the changes to the head and barrel, could the valves have been getting caught on the outer edges of the valve pockets cut/cast into the piston crown? 8 degrees, could the valves have come together and hung up long enough for the piston to hit them?

Very possible...... Nice mess though, I'll bet your little model airplane engines aren't as much fun as this...........

Didn't change the cams at all, standard lift etc. In fact increased clearances a little bit to ensure valve/piston harmony

**Sideways Sam** · 5th January 2009, 16:48

Originally Posted by cmac

I dropped a valve on a Triumph once (at about 80mph on a gravel road

) and the head looked just like this one. The difference was the piston didn't break - the valve ended up welded into the piston!
IMHO I reckon the piston/conrod have been intact with a loose valve head floating around the bore for quite a few revs - though I do acknowledge your comment about the stems/springs etc being intact.

I haven't had much experience with dropped valves but if the retainer is still in place then surely the valve hadn't dropped? maybe the valve-head came off but I think a more likely scenario maybe the piston hit the valve and that caused the head to part company with the stem.......

Lot's of pondering but I should really just go out and buy a new engine!

**speedpro** · 5th January 2009, 17:58

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.

**Kickaha** · 5th January 2009, 18:06

Originally Posted by speedpro

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.

My experience with them (aftermarket) in the GN revving to 12500, was they lasted one and a bit meetings before destroying the engine

The factory Suzuki valves survived two years of getting hammered like that and were one piece

**Sideways Sam** · 5th January 2009, 18:07

Originally Posted by speedpro

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.

Go figure....... you learn something new everyday.

I'm gonna have another look at them now!

Thanks for that

**Pumba** · 5th January 2009, 20:04

Originally Posted by Sideways Sam

Go figure....... you learn something new everyday.

I'm gonna have another look at them now!

Thanks for that

Them? Thought there was only one left

**Sideways Sam** · 5th January 2009, 20:25

Originally Posted by Pumba

Them? Thought there was only one left

Yeah, you've got a point there

**cmac** · 8th January 2009, 09:51

I misspoke when I said the Triumph dropped a valve - it was the valve head that broke off.

**Buckets4Me** · 8th January 2009, 11:35

time to look for a new engine
maby a 2 stroke can be found and fitted to you'r bike

they never have a problem with valves dropping braking or coming into contact with the piston
but you can still make a mess with them

that is one nasty looking mess you call an ex fxr engine

hope you can find something soon to replace it with

**Sideways Sam** · 8th January 2009, 14:21

Originally Posted by Buckets4Me

time to look for a new engine
maby a 2 stroke can be found and fitted to you'r bike

they never have a problem with valves dropping braking or coming into contact with the piston
but you can still make a mess with them

that is one nasty looking mess you call an ex fxr engine

hope you can find something soon to replace it with

I've managed to get another engine so we'll be mobile for the next Mt Wellington meet. Got a second one lined up for a spare. Each of them cost more than the whole bike did originally............ Ouch

Won't trust them till I've pulled them down and blueprinted ........

I just found out today that Ausies are buying FXR engines off NZ wreckers to race!!!!!!!!!! No wonder it's getting hard to find them at the right price.....

Might have to go 2-stroke!!!!!!!!!!! A GP125 in a FXR frame?????

Bloody Hell, might as well go to an auction and buy a bent SV650, it'd be a lot cheaper racing a Pro-Twin