This bike's been great. 8400 miles, started immediately every time, 70 to 80 miles per gallon. The other day I'm riding home from work at 45 miles per hour and the engine just quit. No loud noises or anything. It just quit. I could see plenty of Gas in the tank but when I crank it using the electric starter it sounds like it turning way to fast. It's never sounded that way before. Kind of like there wasn't any compression. I pulled the plug and can feel some "air" coming from the plug hole. I can see spark in the plug gap when cranking but the cranking is too fast and it just doesn't even sound like it wants to start. Any one else have this problem? I'm afraid it's major.

What say ye?

Thanks

Sounds like you may have a timing chain problem. It may have either broken or jumped a couple of teeth on the timing sprocket.

I agree with above,

try readjusting the timing it and making sure the timing chain tensioner is properly adjusted.

I agree with above,

try readjusting the timing it and making sure the timing chain tensioner is properly adjusted.

Thanks Guys.

I didn't even think about the timing chain. It could just break while cruising along? Wouldn't it make a loud noise or grinding sound or some noise if it broke? Anyway, how involved of a repair is "readjusting the timing chain?" I do tune-ups, oil changes and installation of accessories. I've never "tore into" an engine. Do I need a professional?

Thanks again,

Kevin

This bike's been great. 8400 miles, started immediately every time, 70 to 80 miles per gallon. The other day I'm riding home from work at 45 miles per hour and the engine just quit. No loud noises or anything. It just quit. I could see plenty of Gas in the tank but when I crank it using the electric starter it sounds like it turning way to fast. It's never sounded that way before. Kind of like there wasn't any compression. I pulled the plug and can feel some "air" coming from the plug hole. I can see spark in the plug gap when cranking but the cranking is too fast and it just doesn't even sound like it wants to start. Any one else have this problem? I'm afraid it's major.

What say ye?

Thanks

your spark plug is fooked

That'll teach you for doing 45 !!!!!!

Hi

Just a thought - have you checked compression with a gauge? - could be piston damage.

Otherwise if you have changed the plug I go with the timing chain.

your spark plug is fooked

Mechanic found the problem and showed me the pieces. A valve-stem snapped which cracked the guide. The valve traveled down into the piston where damage was done. I'm ordering a new head, piston, valve etc. to the price of $840 dollars including parts and labor. OUCH!

What would cause a valve stem, right up near the top, to just snap off?

Kevin

And there was me just about to shout "broken valve", "BROKEN VALVE". I have two SR125 engines that have broken valves (one broke the inlet, the other the exhauset I think); I've not had this trouble on any other bike I hasten to add.

I wish I knew why they break; mine broke right at the top where the spring retaining washer sits. I can only guess that the frequent banging causes them to work-harden and go brittle. Maybe if the clearance is too wide, they work-harden faster than they should. (My feeler gauges are rusted real bad & I can't tell which is which anymore!)

One of my heads has a damaged valve guide too; maybe this increased the friction on the valve, putting it under more stress. Maybe?

As it was a 20 year old bike, I just threw a new valve in & crossed my fingers. (I.e. ignored the damaged valve guide.) 4 weeks later the camshaft gear slipped, which put the timing WAY out & the piston hit the valve and broke the rocker arm. I could go on ....... it ran out of oil recently & seized ....... How much more can this engine take!!

$840 is a big ouch! Is it not cheaper to get 2nd hand engine? (Hence I now have three engines in various states of disrepair.)

ok well i dnt know much about mechanical faults

but when doing 40mph on my sr, the engine cut out

again no reasons, petrol etc etc was fine

it turned out the ignition barrel was slightly worn and as i had gone over a slight bump it cut the engine

just a thought maybe