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Having Trouble With My Yfzr


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#1 justincoty327

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Posted 31 May 2015 - 07:47 PM

I sent my yfz450r to Kenz for some work. I got bigger cams, port and polish, 1-2-1 head, bored 30 over and bored tb, and 13.1 cp piston. Well when it came here it wouldn't start. I reshimmed the valves and now it'll start but once it gets warmed up it quits and won't start back. Also to get it to start you have to either roll start it or hold the throttle basically wide open. My other add ons is an fci, msd, and full yoshi. Any suggestions? I think it's still the valves not being shimmed right.

#2 central cal 450

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Posted 31 May 2015 - 08:50 PM

Probably not a bad idea to call the builder first with questions after spending some g's for a non running motor...

Reworking the builder's set up might not be the best first step.

#3 06yfz

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Posted 31 May 2015 - 09:12 PM

you mentioned the motor being built by kenz, did you send him the whole bike or just the motor? Have you hit the dyno yet to have it tuned or did kenz send you some baseline maps for the msd. Also what tyson said, have you talked to kenz yet? edit: also if you re-shimmed the valves and you think they're still not right, how do you know they weren't correct in the first place? 


Edited by 06yfz, 31 May 2015 - 09:13 PM.


#4 justincoty327

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Posted 31 May 2015 - 09:31 PM

I've called ken repeatedly. He gives me no help. I sent the motor. It won't run long enough to dyno it. I know the valves were off because they were stuck open and no gas was reaching the cylinder. The spark plug was brand new and had no gas at all on it. I reshimmed it to factory clearance then it started but still won't stay running. Ken just says ride it and it'll straighten out. I said I can't take it off my driveway before it quits and won't start back.

#5 PDX YFZR

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Posted 31 May 2015 - 10:11 PM

Are you getting any flashing engine light sequences? Do you have the throttle body hooked up correctly, did you reconnect the intake air pressure sensor hose? 


Edited by PDX YFZR, 31 May 2015 - 10:15 PM.


#6 06yfz

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Posted 01 June 2015 - 07:43 AM

So the valves were stuck open, what'd you do to solve the no fuel issue? If the valves were stuck open youd have tons of unburnt fuel in the cylinder. Also what cams did he install? Some of the bigger cams require tighter shim specs than stock.



#7 justincoty327

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Posted 01 June 2015 - 11:47 AM

He said they were billet cams but I paid for web cams.. Also there wouldn't be in burnt fuel. Depends on which valves are stuck. The intake wasn't pulling fuel until I changed the shims.

#8 06yfz

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Posted 01 June 2015 - 12:18 PM

Web cams are billet. There would be unburnt fuel in the cylinder either way unless the injector wasnt firing or you had no fuel in the system. regardless of what valves are or arent stuck open, the valves are still gonna open as the motor turns over, the fuel will just wash down the cylinder walls if its not being compressed and burnt. How did you determin that the valves were stuck open? It sounds to me like you have either a timing, fuel or spark issue


Edited by 06yfz, 01 June 2015 - 12:23 PM.


#9 justincoty327

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Posted 01 June 2015 - 01:04 PM

He said they weren't web cams. I know billet is just a type of metal. But he didn't tell me the brand. All I know is when they were shipped to me the valves were all shimmed to different specs. No fuel was getting through the tb to the cylinder. I shimmed the valves to stock specs and it started up right off the bat cold. But when it warms up it will quit unless you keep constant throttle to it. As soon as you let off it quits and won't start for about 20 mins.

#10 badzr2

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Posted 01 June 2015 - 01:10 PM

reshim it back to where it was and see if it still starts?



#11 PDX YFZR

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Posted 01 June 2015 - 02:00 PM

Do you still have your stock cams you can put back in? Do you have access to a stock throttle body you could borrow? are you sure your tank is full and the fuel pump is cycling on and off every time you turn on the key?

Edited by PDX YFZR, 01 June 2015 - 02:02 PM.


#12 justincoty327

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Posted 01 June 2015 - 03:11 PM

He used my stock cam cores, no extra tb, but k do no the fuel pump is working just fine.

#13 justincoty327

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Posted 01 June 2015 - 05:49 PM

Let me clarify I didn't send the entire engine. Just the top end and tb. I just talked to ken and we had some miscommunication. So he gave me some ideas to try out so I'll get to it soon.

#14 06yfz

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Posted 01 June 2015 - 08:11 PM

Good to hear, let us know how it turns out!



#15 justincoty327

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Posted 01 June 2015 - 09:56 PM

I definitely will

#16 badzr2

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Posted 02 June 2015 - 02:17 PM

I would be checking the timing



#17 PDX YFZR

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Posted 02 June 2015 - 02:50 PM

Wonder if Kenz might have set up the exhaust cam in the cam mod position, forgetting it was for a YFZR? 



#18 Morgan

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Posted 02 June 2015 - 05:32 PM

Wonder if Kenz might have set up the exhaust cam in the cam mod position, forgetting it was for a YFZR? 


Says Kenz only did the head and cylinder, they were not the end assembler.

Hopefully, the cam timing was correct to begin with and it didn't bend valves trying to start in an incorrect timing sequence.

#19 beastieboy

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Posted 02 June 2015 - 07:40 PM

Check if the map sensor and tps sensor are plugged into the correct spot my raptor did this once and those two plugs interchange on the rappys and create a similar issue no fuel pump etc

Edited by beastieboy, 02 June 2015 - 07:40 PM.


#20 justincoty327

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Posted 02 June 2015 - 08:43 PM

The cams are timed perfect. On the yfzr as far as I know the sensors cannot be plugged in wrong. But I'm sure it's right by the way I took it off. I'm going to work on it this weekend. By the way I'm not throwing stones at ken guys. His port job looks freaking amazing.




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