Yamaha R6 Forum: YZF-R6 Forums banner
1 - 13 of 13 Posts

·
My R6 eats CBR's
Joined
·
25 Posts
Discussion Starter · #1 ·
Hey guys,

A few months ago I was riding home from work when I heard a loud rattling noise coming from the right side, so I pulled over and listened for a bit. For some reason I turned the engine off to have a look around, couldn't find anything wrong then went to start her again and all that happened was the starter relay clicked and a small short cranking sound. Straight away I thought it was major and I was right...After stripping the bike down, I found the cam chain tensioner had a snapped spring, the cam chain slipped and cylinder 2 intake valves got a beating :( .

Last weekend, being the self-sufficient type I am, I decided to dig out the manual and battle it myself. I replaced all the relevant parts, lapped the valves and adjusted them. Filled the intake and exhaust ports with some solvent...not a drip came through (was well impressed). I got all the sprockets timed perfectly and a new tensioner popped in, cam chain was nice and tight in top and front run with tensioner taking slack from the back. Gave the engine a number of full turns by hand and carefully watched the lobes depressing the valves in sequence just to be sure timing was right.

After I finished assembling the engine, I did an oil and coolant change. Rolled her out of the garage with a fresh charged battery and felt my heart beat strong through my chest as I looked down at her :/.

When I started cranking, it sounded like it was going very smoothly and started to splutter into life, then just before she got herself going, she just gives up and locks up :(. Now, I'm assuming I messed something up and exactly the same thing happened again. I haven't pulled her apart again yet (I'm a bit to upset and stressed atm) but I strongly expect to see the same thing and I'm sure it's only on one cylinder again.

Any suggestions on what I did wrong OR is there something that I may not have checked that could be causing this? Maybe something wrong with the crankshaft? I visually inspected the piston that struck the valves initially with a 10x loupe and couldn't see any scratches or cracks in the surface. The piston rises with piston 3 fine and flush with the mating surface of the engine. I obivously skipped a lot of stages for the sake of minimizing wall of text as much as I could, but feel free to query any steps I may have missed. I have never attempted anything like this before so I could easily have overlooked something. I'm guessing I'm gonna have to strip it down again to confirm what damage has been caused this time, but I've understandably had enough of it atm and thought I'd turn to the real professionals for a little guidance :) . Any suggestions at all are massively appreciated! I really wanna cry right now lol!

Thanks a lot in advance guys

:( :( :( :thumbdown
 

·
Registered
Joined
·
673 Posts
Never messed with the 6's engine, but what about a bent rocker valve rod?
 

·
My R6 eats CBR's
Joined
·
25 Posts
Discussion Starter · #3 ·
Never messed with the 6's engine, but what about a bent rocker valve rod?
Hi mate, thanks for the reply.

I don't know what that part is, could you elaborate a little?




Oh yeah, I forgot to mention. When I finished rebuilding, it wouldn't crank at all. I found that the starter motor died aswell? I took it apart and there was tons of debris from the brushes inside the casing (even some huge chunks) and the electrodes were quite worn. I cleaned it all up inside and tested it without the pinion reducer connected to the crankshaft and it spun very well so put it all back together.

Could the starter motor failing at the same time be of any significance or just a big coincidence that it happened at the same time?

Thanks again
 

·
Registered
Joined
·
183 Posts
What parts did you replace? What did the pistons look like? If the pistons had taken hits which Im assuming they did you take the bottom end apart to see if you bent a rod?
 

·
crashing aint so bad
Joined
·
2,271 Posts
You could always try bump starting it. if you know that the engine would turn freely before, then it's not an interference thing internally then. I would look into the simple things:

Starter, ignition, fuel, and intake. If one of those things is wrong then it won'r run. It sounds to me as if the starter is it?
 

·
My R6 eats CBR's
Joined
·
25 Posts
Discussion Starter · #6 ·
Thanks for the replies guys,

What parts did you replace? What did the pistons look like? If the pistons had taken hits which Im assuming they did you take the bottom end apart to see if you bent a rod?
I replaced the two cylinder #2 intake valves and their respective stem seals, camchain tensioner and the gaskets for everywhere that needed one. The valve guides seemed fine to me, no visible damage, no free play or movement with valve inserted and valves made a perfect seal after lapping.

The pistons looked great to me, couldn't see any cracks or scratches etc and the action looked fine to me. I've attached some pictures and videos for you to see for yourself. The quality of the piston picture is pretty poor but I'm quite sure there was no damage to the surface of any of them, I looked over them with 10x mag.

I only went as far as taking the head off as the pistons and their movement seemed fine to me, if you watch the video I have attached below, is there still any possibility of damage in the bottom end?




You could always try bump starting it. if you know that the engine would turn freely before, then it's not an interference thing internally then. I would look into the simple things:

Starter, ignition, fuel, and intake. If one of those things is wrong then it won'r run. It sounds to me as if the starter is it?
The engine turned freely by hand before I tried starting it. Second try starting I could hear starter trying to move engine but it wouldn't turn. Afterwards, it turns 3/4 crank rotation by hand then stops :( .


Videos:






Pictures:

Initial Damage.



Damage done to valves.



Head after rebuild.



Pistons.
 

·
Spin it upppp
Joined
·
248 Posts
The only thing I could think of in this case would be that the big end bearing on the crank from the affected cylinder ceased. Did you turn it over by hand after the motor was completely back together? Id also still have my questions about the guides after taking that impact but I don't think its affecting the motor not turning over. Alot of times those bearings on the big end though go out shortly after vtp contact if not replaced.
 

·
My R6 eats CBR's
Joined
·
25 Posts
Discussion Starter · #9 ·
The only thing I could think of in this case would be that the big end bearing on the crank from the affected cylinder ceased. Did you turn it over by hand after the motor was completely back together? Id also still have my questions about the guides after taking that impact but I don't think its affecting the motor not turning over. Alot of times those bearings on the big end though go out shortly after vtp contact if not replaced.
The last time I turned it over by hand was in the video I posted above (after valve repair) - so the motor itself was pretty much fully rebuilt, just needed the valve cover, then carbs/hoses etc. Thanks for the tips, I'll bear them in mind when I strip the motor down again this weekend.
 

·
My R6 eats CBR's
Joined
·
25 Posts
Discussion Starter · #13 ·
Hi Guys,

It's been a while, but I found it was the starter motor that had stopped working when I cranked it previously. I stuck a second hand one in and the bike is now running!!!

Only trouble is, now I got a fair bit of white smoke coming out the exhaust when it warms up :( . I'm assuming it's something to do with the head gasket but there's a few things that are confusing me. Firstly, I've taken it for a 15 minute ride and it runs absolutely perfect, very very smooth. I think it's running better than it ever has. It's losing absolutely no coolant or oil as far as I can see. I've had it running for probably about an hour in total (adding up all the times I've had it running). I took the cap off the radiator and revved the bike and the level did not change at all. (when revving, the smoke actually clears up a little bit) .The smoke doesn't smell sweet or burny..it just smells very strong of fuel. There's no oil in the water and the oil seems fine too.

Any suggestions? I'm well confused!

Thanks,
 
1 - 13 of 13 Posts
Top