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Discussion Starter #1
Hi All

Just purchased on 11/2019 and have been riding it around the neighborhood for around 80 miles. Today I took my wife (additional load?) out on it, and decending on a slight down hill with around a 3000rpm engine speed, the engine shut down. Did not start again. Had it picked up and taken home.

What sequence of events does one begin to check/identify to solve this issue. I have a Haynes service and repair manual, but have not come across this shut down issue.

Anyone have the solution?

Thanks in advance

Steve, dirt bike two stroke guy.
 

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First thing to check would be battery voltage. Should be 12.7V or more.

Next thing would be fuel. Old/bad fuel or moisture in the tank. If there's any question, drain the tank. Add a strong fuel system cleaner like Techron Concentrate to clean the injector and intake track.

Air filter and spark plug also, if no success.
 

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Thank you jkv for the reply.

I checked all the error codes first. Nothing showing. Checked spark. Good spark. Then I sprayed ether into the intake. Not even a pop.
Opened the case oil fill cap and while cranking over engine, air was blowing out of the hole.
Compression check showed zero commpression. Yet no noise heard or any siezing while failing on thefinal ride. Never ridden hard by me. Just purchased 11/ 2019.

Turns out the intake valve was stuck open. The valve left a light imprint on the piston. Compression from piston enters the case when valve is stuck open.
Entire intake port and valves had major varnish.
This bike was suppose to have (2013 Repsol) 3,100 miles on it. However, looking inside the intake port and around the valves, it looked like chocolate tar sludge. Hard like expired chocolate. Oddly, the exhaust valves and port was normal.

I bet this bike was left out or not run for years. I think I was suckered a bit. Oh well.

Changing out the valves and parts, and piston/rings. Cylinder was clean and 76mm. For about $150.00 and DIY, I'll have a pretty much new top end.

Steve
 

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Thank you jkv for the reply.

I checked all the error codes first. Nothing showing. Checked spark. Good spark. Then I sprayed ether into the intake. Not even a pop.
Opened the case oil fill cap and while cranking over engine, air was blowing out of the hole.
Compression check showed zero commpression. Yet no noise heard or any siezing while failing on thefinal ride. Never ridden hard by me. Just purchased 11/ 2019.

Turns out the intake valve was stuck open. The valve left a light imprint on the piston. Compression from piston enters the case when valve is stuck open.
Entire intake port and valves had major varnish.
This bike was suppose to have (2013 Repsol) 3,100 miles on it. However, looking inside the intake port and around the valves, it looked like chocolate tar sludge. Hard like expired chocolate. Oddly, the exhaust valves and port was normal.

I bet this bike was left out or not run for years. I think I was suckered a bit. Oh well.

Changing out the valves and parts, and piston/rings. Cylinder was clean and 76mm. For about $150.00 and DIY, I'll have a pretty much new top end.

Steve
Well, that wasn't exactly what I expected to hear...

Glad you got it sorted out.

Not sure how there would be that many deposits in that short of time. I always suggest running Techron Concentrate once per season, which clears any deposits on the valves and chamber. It seems that the CBR has more issues with that than average.

I attribute some of that to low RPM running, though other members have run low RPMs for years without any issues. Getting into the higher RPM range occasionally helps to break loose deposits before they build up. It's possible that in some countries the gas doesn't have adequate detergents to keep deposits to a minimum.
 

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Discussion Starter #6
For off road, I have only 2 stroke. Easy and simple. Mostly a few vintage Elsinores from the 70s. And a 2017 Husky TC 125 incase I want to stop and have suspension that day.
 

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Discussion Starter #7
A few pics from the valve sticking open.
Valve hit piston on a down hill coast. Low rpm, not under any power.
The piston has a hairline fracture at the oiling hole.

Pretty dirty for an engine with 3k on it.
 

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A few pics from the valve sticking open.
Valve hit piston on a down hill coast. Low rpm, not under any power.
The piston has a hairline fracture at the oiling hole.

Pretty dirty for an engine with 3k on it.
Ya it is.

Seem like it was pumping oil into the cylinder to you? That's a lot of wet black deposits.
 

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Discussion Starter #9
I would have to agree with you. Just picked up my order of new cylinder, piston, circlips, rings, valves, valve seals, gaskets. So now I have to assemble the new valves, put in the old shims and see what shims to order for proper clearance. I figure thats how to get the right ones. After lapping them in.

I do have a question that i can't seem to find and answer fo anywhere yet. r. How does one know how much tension to put on the cam chain? Is it adjustable or fixed? Max it out. Mine was way tight.

thanks in advance.

Steve
 

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I would have to agree with you. Just picked up my order of new cylinder, piston, circlips, rings, valves, valve seals, gaskets. So now I have to assemble the new valves, put in the old shims and see what shims to order for proper clearance. I figure thats how to get the right ones. After lapping them in.

I do have a question that i can't seem to find and answer fo anywhere yet. r. How does one know how much tension to put on the cam chain? Is it adjustable or fixed? Max it out. Mine was way tight.

thanks in advance.

Steve
I found that after setting the proper clearances on our CRF150R top-end rebuild I need to run engine briefly, then check the clearances again. They did change. After resetting them they haven't needed further adjustment, and the engine is running near redline all the time.

As for your cam chain tensioner - it should be automatic. Though I do recall some possible issues with the stock tensioner. We have used manual tensioners in other engines, and they needed to be set taught - but not tight.
 

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Discussion Starter #11
Ill make a note of your comments and check the valves after a bit of run time.
I'll check the tensioner and let it do it's thing automatically.

Thanks again

Steve
 

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You may want to check around here a bit for info on problems with the stock tensioner.

If they are not expensive it may be a good time to just replace it - if you think it could have issues.
 

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Just pure speculation, but from what I read I'm thinking the previous owner had to change out the instrument cluster. Of course that resets the odometer back to zero. I had this done when my 2011 cluster was blinking at me and it was a manufacturer defect. Had 8k miles at the time and it reset to zero.
 

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Discussion Starter #14
I thought about the instrument change out also. Could be. The original tires are still on it with most of it's tread in good shape. Although the side walls are cracked. I have a new set to install this week.

I would bet it sat outdoors for years after being abused.

But it has cleaned up nicely. Like new at this point. I'll post a pic later.
 

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Discussion Starter #15
Be the way. The most difficult part of this repair was trying to put the 2 rubber shields under the gas tank back. What a challenging thing the installation is.

Should have made a vid on that part.
 
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