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Discussion Starter · #1 ·
Hi Guys,

New to the forum from the UK. I have been a long time browser though when I had my 660 a few years a go. Anyway I recently purchased 700 that was fitted with a Yakahosu turbo kit. Sadly it was from a garage that deals with bikes and the mechanics having no clue admitted to me that they had been messing with the waste gate to alter the boost. Not knowing much about it myself, I still bought the thing and it ran very well after some light fondling... for a week or so any way.

Bike cut out, made a clunk and kind of almost locked the rear wheels as I was going Vmax on an open road overtaking a car. Pulled the clutch in and free wheeled to the side of the road to get recovered. I get an error code on the dash of one long blink and 4 short (intake pressure sensor) but I have checked all the hoses and leads to the sensor and all seems fine. The bike will not push in top gear so I can only assume its piston/crank related. I attempted to check the oil the day after but obviously it hadn't been warmed up so I don't know how accurate the oil level would have been but seemed to be some in the tank but when I drain it later I guess i'll find out.

My problem now is, although I feel handy enough to fix it myself... what should I be buying to replace these parts? if it needs a new cylinder would I be best going larger bore with a piston with a lower compression? or just replace with stock parts, maybe a stronger rod?

does anybody have yakahosu installation instructions also? there website is still down for construction or perhaps they have folded. I can only assume the oil may now need to be different and more of it but cant find any information anywhere about it

any help would be much appreciated. will post pics when I get the head off it tonight.
 

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Discussion Starter · #2 ·
Soo got round to taking the head off last night and as suspected there was carnage. not certain of the exact reason for failure but the rod has ripped the bottom of the piston off but not before smashing it off the head, probably bending the valves and scouring the hell out of the cylinder.

so I have accepted I possibly need a new head, cylinder, piston and rod but im just hoping that the other pieces off the piston have caused any damage to the bottom end when they fell in. I will need to investigate this evening when I get the engine out and onto a workbench.




 

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Thanks for the pictures. Wow! I never heard of this tyoe of failure where the wristpin gets ripped out if the piston! So the piston must have seized tight in the cylinder?

Sent from my GT-P7500 using Tapatalk 2
 

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Discussion Starter · #4 ·
Thanks for the pictures. Wow! I never heard of this tyoe of failure where the wristpin gets ripped out if the piston! So the piston must have seized tight in the cylinder?

Sent from my GT-P7500 using Tapatalk 2
funny thing is, the piston isn't stuck that hard in, I just left it in for the pictures.

I have decided to take the whole lot to an engine builder that I am lucky to have local to me. see if he can salvage any of it.
 

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Please let us know and keep updating. Very sorry to hear about your misfortune though.

Sent from my GT-P7500 using Tapatalk 2
 

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Wow, that sucks. Best part is now you can build it your way and know its done right!
 

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Discussion Starter · #7 ·
Wow, that sucks. Best part is now you can build it your way and know its done right!
ha, yes and no. I only have basic knowledge of engines. I can strip one and pop it back together with standard parts and a good workshop manual no problem but when it comes to possible changing compression ratios and different cams etc.... oh and the fact that mine has a turbo bolted to it and 10 times more electrics.... I'm clueless. will pop it round to the engine builder this weekend and let him have a look. he has built a few turbo busa motorcycles so he will know more than me.

will keep you all posted with the progress

thanks
 

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The head looks repairable. Might as well have a little porting done while its apart and a good set of alive springs I your gonna run turbo again. The crank I'm sure is trashed which doesn't matter because they are trash from the start. Get a 5mm put in it with a good clutch and a cp piston. Then with the new head work and mate a small cam it would run great na and even enter with a turbo. But IMO that turbo isn't good anyway, I'd sell it and stay na or get a better kit. Also stay stock bore if ur not drag racing. Not worth the problems
 

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Discussion Starter · #10 ·
Update! sorry, been a long time since i posted this thread. I did eventually get the bike back. It ran a little rougher than before i blew it up, lots of back fires on the over run, bit rough at low speeds but hey, it was fixed.

I now have another issue i'm hoping you can help with. just recently the bike has broken again, whenever i try to give it a decent amount of throttle, it dies, a little splutter but it just seems to die, i let of the throttle a bit and it carrys on no problem.

the comapny that installed the turbo to the quad many years ago say that its the spark plug gap and that i need to make it paper thin. Tried this and still have the same issue. Although the new plug i tried it with did stop the back fires. I'm thinking it may be the TPS or maybe the second injectors controller? A mate of mine has tried to tell me its the actuator?

Any ideas?
 

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Start with dropping the heat range of the spark plug. A NGK CR9EK is a good plug. Then you need to establish what the air fuel ratio is. So spark plug reading or a o2 gauge is in order.
By the looks of your earlier photos the engine had high cylinder pressure . I would recommend trying to get the air fuel ratio a bit rich . Around 12.5-1 would be a good start.

While you are doing all of this check the TPS it should be around .63-.73 volts closed . I set mine at .68.

This will give you a good starting point to diagnose if there is another problem going on.
 

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Discussion Starter · #12 ·
Thanks for your reply. I had a suspicion it may be the TPS so i till try that first. I am using a CR9EK plug already, has worked fine since ive had it. replaced it when it started misbehaving and it did make it run smoother but still doesnt run with any power. I will have to get an air fuel sensor welded into the exhaust. will keep you posted
 
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