Back Cylinder out with a BANG!

Hey folks,

Bit of a dilemma.... Recently after a 30min run on a cold night, I stopped off for fuel.

On restarting the engine shot up too 4/5k revs and promptly gave the loudest back-fire I've ever heard (I swear the folks in the petrol station thought about ducking incase there was a second shot)... so it was a blagged AA trip home for me.

Anyways,

On later inspection, the engine would start (reluctantly with only the front cylinder).
The back cylinder's spark plug IS firing.

On turning the engine over with both spark plugs out... it sounds mechanically fine.

Please any ideas??? (I'm way to skint to take it to a garage if this is a simple case of fitting a new part).


Searching the forum I've not found anything too similar:

Possibly the back cylinder injector or coils perhaps??

Any advice would be much appreciated.

Thanks

[TSM]

Can you get injectors jammed open?

A plug that sparks out of the engine doesn't mean it will spark when installed. Try a new set of plugs first - or at least one.

Look under the air box to see if the rubber mount to the rear cylinder hasn't blown off.

Thanks for the info so far:

Already tested it with the spark plug from the front cylinder, but no joy .

I'll have a ratch under the airbox and look for the rubber mount as suggested, and also then I'll have a look at the injectors...

I'm guessing from the manual that the injectors are modules, so i could swap the front (working one) to the back and give it a go??

**really wishing i had done that bike repairing course now**
**and had my own break down (not having to pretend to be someone )**

If i can work it out this week then i'll have a look at the MCN bike show for bits and bobs to fix it (hopefully).

Originally Posted by Sponge

Thanks for the info so far:

Already tested it with the spark plug from the front cylinder, but no joy .

I'll have a ratch under the airbox and look for the rubber mount as suggested, and also then I'll have a look at the injectors...

I'm guessing from the manual that the injectors are modules, so i could swap the front (working one) to the back and give it a go??

Take the air box off, you will see your throttle bodies. As chewey says makes sure that the rear one is on. You can run it (carefully) for testing without the air box, i.e. don’t ride it like that.

If you want to test the injectors one way is take off the throttle bodies, and put a piece of paper or tissue paper under them and turn the key on (fuel system primes and squirts some petrol in. Or hit the starter and check. Keep in mind the paper will only tell you if petrol is getting through not if one injector isn’t misting properly. If they are throwing out the same amount and it’s the same sort of mist that might not be the problem. (Remember, 3 things, petrol, air, spark (at the right time!))

As you suggested the injectors are the same for both the front and back and you can swap them, but be careful. Tiny bits of dirt/dust can block them, only do this once you are sure before buying one.

Also grab a copy of the online service manual and keep a very close eye on it if your not too experienced. Oh and be VERY careful with running the bike and playing with the throttle bodies/engine/etc. Don’t just think I’ll push that in now, because it might just work a bit too well, i had a bit of an intimate early detonation experience with my sv that I wouldn’t to repeat. Almost blew me hand off!

Oh and above is just from one sv rebuild experience, im not a mechanic or other qualified engine fiddler, so take what i have put with some common sense for best results. And im sure someone will be along to tell me off/correct me shortly...

http://www.dansmc.com/ is also a good resource for motorcycle repair information, however it is mainly related to older machines.

Progress report please

Well 'had a go' this weekend.

Thanks to 'Sudoxe' and his great instructions I managed to check that both injectors are infact working fine....

Put the bike all back together, and it fired up perfectly.

I've had a couple of days smooth running and smooth starts. However there was quite a strong smell of fuel, so I tightened the throttle body mounts a little more and that seems to have stopped that problem.


Current State:

Well pulling up to stop at traffic lights, and the throttle is let go, it drops to about idle speed and just cuts out ( ). Its not actually stalling as the clutch is fully in. On restarting it has on occasion had the same 'back cylinder not firing' issue, but after giving it a little more throttle it eventually fires up.. and back to normal. I can cope with it .. Except this morning on just pulling onto a round about and frantically trying to start it on the move…

On sitting in neutral, if the throttle is blip'd atall it will cut out, and if the throttle is rolled on and off, again it will cut out… perhaps I've knocked the idle setting? (although it is still idle'ing at 1k which I thought was normal (assuming the choke's turned off)).

I'm just starting to despair with it… think I'll have to save up and go to a garage. I always find going to a mechanic with an intermittent problem is always

Or perhaps try a part exchange (since it seems to work 80% of the time right now)??

[Viney]

Did you install a brand new set of plugs?

The idle should be slighyl higher 12-1500 i seem to remeber?

Glad i helped someone not destory there bike though!

Dan