Dead Kat

[Nigkat]

Out for a ride this evening, running fine. Overtaking a car suddenly lost power.  Running poorly on 2 cylinders, 2 and 3, with a very buzzy noisy. Limped home and died just as I stopped. Tried to start it and sounds very grauncy, like cam chain is very loose. stopped  straight away trying.  Removed spark plugs from 1 and 4, both look OK just a bit wet. 

Any thoughts before I start to take things apart? 

Cheers 

[johnr]

dont try to run it.
get the plugs out and see if it sparks on all four when its turning over. if its 2+3 then they share a coil, so it would be buzzy going home cos it was carrying two dead cylinders. id start with electrics first cos of the fact that two cylinders on the same coil have gone off.
 

[Nigkat]

5 minutes ago, johnr said:

dont try to run it.
get the plugs out and see if it sparks on all four when its turning over. if its 2+3 then they share a coil, so it would be buzzy going home cos it was carrying two dead cylinders. id start with electrics first cos of the fact that two cylinders on the same coil have gone off.
 

Yeah cheers John, was going to be the first thing to look at but more concerned about the noise it made trying to turn it over. 

[johnr]

its cos two cylinders are trying to carry the other two. pull out all 4 plugs, that way when you spin it over youre not fighting compression and you can see whats sparking and whats not. it might be something daft like a broken wire or bad earth.

[Nigkat]

OK thanks I'll give it a go. 

[Suzukian]

Turn it over with the spark plugs out, and do it by hand. so you can feel if anything has broken inside.  This will minimize any damage and possibly prevent catastrophic damage.  You can check the spark with all the plugs out, but do it by hand off, once you determine the engine is turning over smoothly, then you can turn it over with the starter, you may have dropped a coil.    You will have to take off one of the crankshaft covers, the right side, sitting on the bike, has the electronics, so you won't have oil coming out.  Check to make sure.

[Nigkat]

Found the problem. Rear cam chain guide snapped in 2 places. All the inlet valves are sitting proud and a few marks on top of the pistons. 

Hopefully there won't be to much damage to guides and seats. 

[DaveV65]

NigKat, will the inlet valves sit flush with the cam turned away from the follower? You may have bent a couple, as you say the pistons have been kissed and there's witness marks on the valves.

[Nigkat]

Stripped the head and all the inlet valves are bent. Seats look OK, just need to check the guides to see if they are worn by the bent valves. Hopefully not. What is the best way to check?

Think I'll replace the cam chain. Don't really want to split the bottom cases.  What do you think about replacing with a riveted up chain or bite the bullet and replace with new endless one? 

[TonyGee]

a riveted cam chain is perfectly fine if done correctly 

[johnr]

44 minutes ago, TonyGee said:

a riveted cam chain is perfectly fine if done correctly 

yep, perfectly acceptable  to use a rivetted link. have you got valves?

[Nigkat]

OK thanks and no not got any valves. Think mine are+ 1mm but will have to check. 

What is the std. Inlet valve size? 

[johnr]

I think abuso valves are sold on Eblag in 1mm oversized.

[Nigkat]

21 hours ago, johnr said:

I think abuso valves are sold on Eblag in 1mm oversized.

Cheers I'll have a look. 

[Nigkat]

Never heard of them before but look like just the job. They are + 1.5 mm. Very reasonably priced to, might even treat myself to some titanium retainers if I don't find anything else wrong. 

[Nigkat]

My bent inlet valves were 27.5mm. I thought I had found a set, specified that I needed 27.5mm dial. I have received 27mm ones. 

The supplier says that they are fine. But will the seats need recutting or will they lap in OK? If they need recutting I might as well go slightly larger. 

??