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Hard to start / high compression

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Hi peeps

Been out in some local woods today and as ever, the RM-Z is giving me back chat!!

I was turning around in double track section so slowed down considerably then as I went to put the power down to accelerate it cut out on me. I don't know if I stalled it, or the bike cut out or what but when I tried to kick it over it was a hell of a lot harder to kick. Thinking I was just tired I found a tree to prop myself up on but the compression was so much I felt I could stand on the kick without it moving???? If I kept pressure on it would pass through TDC but when TDC came round again it was ridiculously hard. Tried to bump start it to no avail, but to be fair, it was a half arsed attempt. Ended up doing the walk of shame back to the van and bringing it home.

Which gets me to now, I've pulled the plug out and it turns over pretty easy, easy enough to do it by hand. No petrol/oil/water came out when I did this. Plug back in, hard again. Took the head off, all 4 valves move freely and spring back nice. Turned it over with the head off and it's the 2 exhaust valves when it stiffens right up.

Jobs I've done recently, had the shop clean the carb and rejet to oem(I've had loadsa issues with it bogging at 1/2 revs) Changed the coolant, topped the oil off(up to the little drain screw on side casing) Adjusted chain tensioner(followed sticky on here, found TDC lining up dots, released tensioner then tightened back up)

I'm now at my wits end lol

Anybody, any suggestions? I'm thinking of finding a big hill tomorrow and seeing it I can bump it with a bit of effort, would this suggest the decomp?

Thanks in advance and sorry for all the blabber above, just wanted to give all info 🙂

Cheers

Mark

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Hi peeps

Been out in some local woods today and as ever, the RM-Z is giving me back chat!!

I was turning around in double track section so slowed down considerably then as I went to put the power down to accelerate it cut out on me. I don't know if I stalled it, or the bike cut out or what but when I tried to kick it over it was a hell of a lot harder to kick. Thinking I was just tired I found a tree to prop myself up on but the compression was so much I felt I could stand on the kick without it moving???? If I kept pressure on it would pass through TDC but when TDC came round again it was ridiculously hard. Tried to bump start it to no avail, but to be fair, it was a half arsed attempt. Ended up doing the walk of shame back to the van and bringing it home.

Which gets me to now, I've pulled the plug out and it turns over pretty easy, easy enough to do it by hand. No petrol/oil/water came out when I did this. Plug back in, hard again. Took the head off, all 4 valves move freely and spring back nice. Turned it over with the head off and it's the 2 exhaust valves when it stiffens right up.

Jobs I've done recently, had the shop clean the carb and rejet to oem(I've had loadsa issues with it bogging at 1/2 revs) Changed the coolant, topped the oil off(up to the little drain screw on side casing) Adjusted chain tensioner(followed sticky on here, found TDC lining up dots, released tensioner then tightened back up)

I'm now at my wits end lol

Anybody, any suggestions? I'm thinking of finding a big hill tomorrow and seeing it I can bump it with a bit of effort, would this suggest the decomp?

Thanks in advance and sorry for all the blabber above, just wanted to give all info 🙂

Cheers

Mark

What year is it and do you have an idea of how many hours are on it ?

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Decomp failed. Open it up and check the spring. Then fish out the pieces from the oil sump screen. Pretty easy fix just make sure you find all the pieces of the old spring. Slap on a new spring and your good to go.

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Thanks for the replies, it's a 06 and I'm not too sure on hours.

Is this a engine out job? Easy enough for a home mechanic or shall I put it in a shop?

Edited by Marko369

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Should be an easy fix. Remove the left side cover and flywheel then find the sump screen and remove the old spring. Install a new spring on the camshaft decomp and your good to go.

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Great news, thanks again for the info mediaht  :cheers:  

 

I've had the head off and can see what I think is the decomp at the end of the exhaust cam, does this sound correct? If so, I've looked on the TT OEM parts part of the website and cant seem to see this bit on the exploded diagram? Obviously being from the wrong side of the pond  :uk: I'm not going to order from TT but I do need the part number for the spring, can anybody help?

 

Cheers

 

Mark

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First make sure the spring is the issue. If the head is off then look at the exhaust cam. On the outside of the sprocket there is a little weight that is attached to the decomp button on the cam lobe. When the motor is off the little spring is used to return the weight and push the button into the bucket slightly opening the valve for decomp. If the cam is in your hand, just move the weight back and forth to see if it returns the button. I am assuming this is your issue from what you said in above posts, however without seeing it myself I am taking a best guess of course. You will have to confirm that this is your issue before you invest in new parts.

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Checked again and the weight I'm talking about has a spring on, that's snapped! I've manually moved said weight and it 'decompresses' allowing me to kick it over easily(well as easy as these things are to kick lol) So it is indeed the spring that's required, bravo mediaht :beers:

So, where do I get one and does anybody have a link to where I can find the part no please :D

image.jpeg

Edited by Marko369

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Cool. When you pull off the spring, make sure all the pieces are there. If not there in the sump screen. Get them out so they don't make there way to the oil pump. Should be able to get the spring at any dealer. We run our motors at extreme rpm (rev limiter) and the springs come apart very often on our motors. It's kinda a normal thing in the Flattrack world. Some guys just remove the whole decomp device and push start there bike. In the motocross world it's not very common so you should be fine with just a new spring and a lot more miles. Good luck.

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