Ideal Top End Rebuild

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skyler914

New Member
May 8, 2013
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I went out riding today and about 45 minuets into it my '04 blaster lost some serious power. It started smoking and barely had enough to reach the top of the rpm range in Neutral. So I'm thinking I need to rebuild the top...

My question to you guys is: what would be the ideal way to go about rebuilding it, modification wise.

When I ride its typically trails through the woods with some decent hills, so I guess I'd be looking to maximize the torque throughout the rpm range. As far as I know the only thing that was done to the bike before I bought it was that the TORS was removed.

If you could point me in the right direction, I'd appreciate it. thanks.
 
Just because it started smoking and losing power does not mean the top end needs rebuilt. I would think you need a clutch side crank seal. Was it white smoke? Did it stink?
 
You should find out why first. If your running the wrong jetting or have an air leak, you will just burn up your new top end. Do a compression and leak down test first. You may just have blown a crank seal and the top end MAYBE ok.
 
My other reason for thinking rebuild is because when its running its leaking oil from the base of the head. You can also feel exhaust gas escaping from the same hole.
 
I bought the bike for 350 with this problem. My intention was to run it until it needed to be rebuilt and then upgrade in the process. And now I believe it's time for a rebuilt. I've got a budget for this project of $500. I've heard that boring doesn't do a whole lot, so I was thinking about porting.
 
You are correct as to boreing in and of itsself doesn't add much. However if you are spending money on porting a fresh bore is the best way to go. Highly suggest doing a leak test before disassembly.

Possibly fixing the base gasket leak might have made rebuild unneeded, never know now.
 
Larry's Shee said:
Possibly fixing the base gasket leak might have made rebuild unneeded, never know now.
Click to expand...

I haven't started anything yet. So there's still time. This only happened yesterday. I think maybe I'll give that base gasket a shot and see if that works. Who knows, if that works, maybe it'll give me time to be able to up budget.

I am still wondering, though, what are the best mods for the top end. If I do end up porting it, what size? Does this effect the engine negatively in the long run?

If boring and porting go together, what do I bore it to, to be able to get some more power with the port job. Does boring make it run hotter to the point where it could seize the whole engine?
 
As long as the jetting is correct, no mod will cause destruction.

If you have an after market pipe already go for a re chambered head as as your next upgrade.

Unless you go big bore 240cc, stock boring will give you very, very little increase in power if any.
 
Just thought I'd post an update.

Pulled the top end off this afternoon. What I found may be the result of my oil pump going bad or clogging up. The sleeve has got some decent gouges in it. The piston has the same gouges and is missing a piston ring while the other ring looked like it had been shaved down flat with the piston. I spoke with with Ken from Ken Oconnor Racing and he said that at least the piston didn't crack and fall into the bottom end.

looks like sometime next week I'll be shipping my engine to him so he can work his magic. any suggestions?
 
skyler914 said:
I spoke with with Ken from Ken Oconnor Racing and he said that at least the piston didn't crack and fall into the bottom end.

looks like sometime next week I'll be shipping my engine to him so he can work his magic.

any suggestions?
Click to expand...

wise choice !

when you get it back....
assemble and install it,
leakdown test it.
ditch the oil injection and mix 32:1 with a good 2 stroke oil..... ken, myself and many others prefer maxima super M
do the proper heat cycles then retorque the head and base bolts....
http://www.blasterforum.com/engine-13/blaster-engine-break-44174/
no sustained wide open throttle runs for a tank or 2 of fuel.
do your main jet plug chops to confirm jetting.
then ride it like you stole it I:I
 
Wise choice calling Ken. I just got mine back from him and it rips. Get the trail porting and the head mod, you wont be disappointed. When you get it back hang on tightly, the new power will suprise you.
 
bummer981 said:
Wise choice calling Ken. I just got mine back from him and it rips. Get the trail porting and the head mod, you wont be disappointed. When you get it back hang on tightly, the new power will suprise you.
Click to expand...

i kept asking him /\ all weekend what he was smiling about everytime we stopped for a break, his answer was always the same...... "I can't believe the power difference" I:I
 
skyler914 said:
Just thought I'd post an update.

Pulled the top end off this afternoon. What I found may be the result of my oil pump going bad or clogging up. The sleeve has got some decent gouges in it. The piston has the same gouges and is missing a piston ring while the other ring looked like it had been shaved down flat with the piston. I spoke with with Ken from Ken Oconnor Racing and he said that at least the piston didn't crack and fall into the bottom end.

looks like sometime next week I'll be shipping my engine to him so he can work his magic. any suggestions?
Click to expand...

Firstly let me state that I am in favour with you ditching the pump and pre mixing..

But before you lay the blame on the poor old oil pump are you sure that the carnage was not caused by detonation/overheating caused by an air leak.

Whatever you do before you start the motor after rebuild, check for air leaks.
 
Blaaster said:
Firstly let me state that I am in favour with you ditching the pump and pre mixing..

But before you lay the blame on the poor old oil pump are you sure that the carnage was not caused by detonation/overheating caused by an air leak.

Whatever you do before you start the motor after rebuild, check for air leaks.
Click to expand...

After I posted I was doing a bit more research on kens site and came across a section on head gasket failure. It fit the description perfectly. regardless, the pump has to go.
 
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