At 80 mph engine died, hit kill switch and pulled in clutch, got recovered home. On inspection Spark plug electrode smashed. Shone light through plug hole and there was something sitting on top of the piston.

Strip cylinder head off to find one exhaust valve broken at foot of stem and the valve has smashed top of piston and gouged the inside of cylinder head.

Not the sort of thing you expect from an engine that has only done 19,669 miles especially a low revver like a savage.

This has never happened to me before and I have had loads of old bikes and cars over the last 30 odd years.

On inspectiuon the middle of the stem looks like there could be a mafacturing flaw that was impossible to see before stem broke.

Anyone else had this problem before?

I am buying a second hand engine to get bike back on road, should I fit new valves, or do you'se think I just been unlucky and had a 1 in a million stroke of bad luck? The replacement is costing me £400 (about $800 dollars so I don't want that wrecked as well!!!)

Yes cam cahin was still fine. Engine still turned np problem and internals all ok apart from damage to piston and bottom of cylinder head from the end of the valve when piston topped out.

T Mack 1 - FSO wrote on 05/07/08 at 12:06:31:

Are you thinking the engine was running lean and hotter than normal?

Keith_T wrote on 05/07/08 at 12:37:36:


Well....  the second question would be to ask if he had changed pipe or air fitler to a hi-perf type.........  

sounds like a raask pipe

Thinking like Reelthing, I suspect your pipe is a Raask; which is a good thing (wish I had one) as long as the carb is tuned properly to it.

As you do your re-assembly, take note of the carb adjustments and jetting, as there may be some tweaking you will want to do. For one thing, having to have your idle air/fuel screw out more than 3 turns makes me think you may need a larger jet in that circuit, and perhaps a larger main also. (Even despite the year of the bike, it's possible that someone else has been in there before and done god knows what to the carb. Better to go through it yourself and KNOW what you have in it!

Personally, being an air cooled engine and all, I prefer to run bikes a bit on the rich side for just the heating reasons someone else already stated. As long as plugs don't foul!

Good (better) luck!

John

THX for all this real good info guys.

I have an original Suzuki manul for 86 model with 87, 88, update info.
Also I have a clymer manual.

Both say my model has 155 main jet as standard and the US model has a 133 main jet!
So you folk in the US have a much leaner set up from the manufacturer.

It also says for my model (86 to 88) that the base setting for the idle jet screw, (which does not have a plug in it), is 3 and a 1/4 turns out.
The bike was idling nice at that setting and pulled away sweet.

I have checked the size of hole in my main jet and couldn't get a 1.5mm drill through it!!!

So when I bought mine it had a nice Raask exhaust on it, (I have looked at pictures on the net and it is a Raask), which is good.
But it seems whoever fitted it didn't put in a bigger jet, VERY BAD!

Something else I just thought of is that back in the days when this engine was designed we had lead added to our petrol, nowadays we have unleaded 95 octane in the UK which does run hotter than the old leaded used to!

So mine is gonna get a 165 main jet, with the same pilot / idle jet left in, as it must have been running far to lean at high throttle openings.

Just a thought for you chaps in the USA, over here the emissions are checked for car annual MOT checks, but motorcycles don't get tested for emmissions!
So we can jet richer than standard.

I don't know if the same applies to guys?

If I was in the USA knowing what I have dicovered from this thread I think I would run a bigger main jet and put up with a slightly reduced range, then if they do check emmisions over there put in a smaller jet just for the annual MOT, (or whatever it is you have ), and ride easy to the test station.

I am now convinced that my exhaust valve failed because the engine was running to lean when at high throttle openings, and I will be running richer with my replacement engine.

Thanks to all who have replied to this thread.

I think moral of this one is if you want to avoid the risk of losing an exhaust valve and trashing your engines piston and top end like happened to me, make sure your main jet is big enough. European spec that means at least a 155 main jet.

many thanks to all who have replied on this thread it has helped me suss what happened and I should be able to prevent a recurrence.
Might help others who read it as well.

I was just thinking..... You were running a 20 year old engine with 20,000 miles on the odometer at near full throttle for an extended period of time and you broke a valve.  Sounds to me that you were going to break something sooner or later anyway....  Thats a heck of a load to put on any engine, let alone one as old and well worn as yours..