More info on the Chinese Blaster cylinder

[OConnor Racing]

As the debate about the Chinese Blaster cylinders rolls on, we at KOR have decided to do some proactive research on them. We already know a few things about them. The supplied pistons, top end bearings, and gaskets are absolute garbage. The liners are soft and can be porous on some of them. The cylinder is 10 ounces heavier than a stock cylinder. The port specs are different. The ports need to be chamfered as they don't do this at the factory. The piston to cylinder clearance needs to be checked. My great friend Ron Bushey is running one of these beauties on his sons Blaster. He bought the Blaster with the cylinder already installed. It was loud so we pulled it. We ported the cylinder and modified the head to our normal trail ride specs. We also changed the top end bearing, used OE Yamaha gaskets, bored the cylinder, and installed a Wiseco piston and set the clearance at .003”. The flywheel was lightened and the jetting is spot on. Currently, it's running like a scalded dog. For those of you that don't know Ron, he's a factory mechanic with deep roots at Pro Circuit. He's worked at the highest levels of this sport with some of the best riders in the country. His son is a sponsored rider at KOR and has been beating this bike like an ugly step child for the past few weeks. So far, (20 hours) no problems. I'll continue to keep you informed of the longevity and performance of these cylinders. If this thing holds up as well as a OE cylinder (it won't), you really need to consider the amount of work and parts that went into it. In my opinion, you're buying a cylinder that needs work for $100 and it's substandard to Yamahas product. I understand how these kits can look very appealing to the budget savvy rider but personally I don't see the value when you consider all of the work and parts you need to buy. Stay tuned.

 

[speedyslyder]

excellent work ken.

 

[best]

One place these might be useful is for experimentation. To develop things like porting or the perfect sized Boyesen ports or altered timing or triple exhaust ports without risking a more expensive cylinder. I've been doing basic 2 stroke experimentation on Chinese motorized bicycle engines as top ends are only about $40.

I've been using Blaster cylinders on their last bore for this sort of experimentation, then if it works, carry it over to a good cylinder. If the Chinese cylinder cast iron flakes off or the piston shatters, it would be poor economy.

 

[joeak47]

Thanks to Ken and Steve!
This is how things are learned. You can always do goofy things to the cylinder too, like saw one in half then quarter it like I did. I wouldn't feel so bad with the chinese one. The Yamaha one I took the saw to snagged a ring really bad, so no great loss.

I'm interested to see the outcome of this chinese cylinder.

Steve, those bicycle engines look fun! How much power do they produce? I wonder what other fun things you could power with one? It has me thinking.
A good place to see motorized bicycles, engines and parts is staton-inc.com
Lots of cool stuff on there!

 

[Tooloose]

I'm trying my first Chinese top end build. I've left nothing to chance that my 45 years of expert
repair of multiple brands of 2-strokes engines, everything from porting, polishing, balancing and blue printing ,and so on. Stay tuned for the next 20 hours of correct breakin.Time will tell whether or not China can cast a cylinder, piston and top end bearing that can be purchased for less than $100.00,that will hold up under normal riding,yes I said normal use, not abuse. I used every part in the supplied kit. Replaced all gaskets, and crank seals. Diassembled, cleaned, spec checked all parts for wear and clearances. The ring end gap is @.009 when it put together which is middle of factory specs according to Yamaha.

 

[best]

Joe, they produce about 2hp plus or minus 1/2hp. Stock their output is quite variable due to different manufacturing tolerances from differing manufacturers. The early ones (2010-2013) were not balanced well and only reved to 6000 rpm. I got 1000 miles of often 10,000 rpm at probably about 4hp without even a tuned pipe on my 2015 Grubee Skyhawk 66cc. I suspect I will be able to get 8-10hp out of it with more work and when I put a tuned pipe on it.

The amazing thing is being able to get a very linear torque curve out of these tiny motors. Consider having only one gear, pull away on the clutch at 500rpm, accelerate to 40mph at 10,000rpm, cruise there for an hour, then climb a steep hill at 25-35mph. I find that amazing for a 66cc motor.

Most of this has been accomplished with a smaller squish area than we are used to using on the Blaster. The port timing is very conservative compared to the Blaster. Need the swept area for torque. Compression is still important, but too much causes problem with the thin chrome cylinder plating. Making the ports wide and tapered at top on exhaust the key to more torque and power and rpm.

Keeping the port area consistent very important, equal to diameter 15mm on intake and diameter 19 on exhaust. Case stuffing gained low rpm torque at the expense of rpm. It is a balance to maintain both. To be honest, in the end I marvel at what the Chinese engineers have done with this motor.

Steve

 

[joeak47]

How much do they weigh? Neat looking.

 

[joeak47]

I'm trying my first Chinese top end build. I've left nothing to chance that my 45 years of expert
repair of multiple brands of 2-strokes engines, everything from porting, polishing, balancing and blue printing ,and so on. Stay tuned for the next 20 hours of correct breakin.Time will tell whether or not China can cast a cylinder, piston and top end bearing that can be purchased for less than $100.00,that will hold up under normal riding,yes I said normal use, not abuse. I used every part in the supplied kit. Replaced all gaskets, and crank seals. Diassembled, cleaned, spec checked all parts for wear and clearances. The ring end gap is @.009 when it put together which is middle of factory specs according to Yamaha.

Did you at least chamfer the ports? That's one of the biggest issues they have. Looking forward to your test.

 

[Tooloose]

Did you at least chamfer the ports? That's one of the biggest issues they have. Looking forward to your test.

The ports were chamfered and polished. All slagg removed and ports matched the full piston sizes . Transfer ports stretched down as I felt comfortable the only thing I didn't do is mill another .004 off the bottom of the cylinder. That would really set her on go

 

[OConnor Racing]

22.5 hours on it now. 150# static compression.

 

[suprex]

Any updates on the Chinese cast cylinder?

Thanks.

 

[Markblaster]

It has blown up shooting the head off the engine crashing thought the tank and into his face. JK

Any updates?

 

[OConnor Racing]

50 + hours.

 

[Tooloose]

Knockon wood! Still running just finished breakin period

 

[RomP]

Interested in the outcome.. Any news, 2 yrs later ?

 

[best]

I have one on a Blaster I bought last year. Engine was noisy, sounded like piston slap so I pulled the cylinder to have a look. Piston clearance was acceptable but it was obviously a very cheap quality piston in a stock bore Chinese cylinder. Put it back together as is and still running it. Compression is low and it is noisy but it runs. Not impressed. Going to replace it when I get a few other projects done.

This is my "guest" 4 wheeler for gentle running. Just by the looks of the piston alone I would not run this engine hard. My guess is that it would break a skirt with much hard running.

 

[RomP]

I have one on a Blaster I bought last year. Engine was noisy, sounded like piston slap so I pulled the cylinder to have a look. Piston clearance was acceptable but it was obviously a very cheap quality piston in a stock bore Chinese cylinder. Put it back together as is and still running it. Compression is low and it is noisy but it runs. Not impressed. Going to replace it when I get a few other projects done.

This is my "guest" 4 wheeler for gentle running. Just by the looks of the piston alone I would not run this engine hard. My guess is that it would break a skirt with much hard running.

Thanks for the feedback. OEM parts are unrealistically expensive down here in SA. New Cylinder kit cost more than what the bikes sell for. Many of these Chinese kits have been sold here and not to sure how long they have lasted. cant get much feedback locally. I have a spare motor to rebuild and was thinking of this as an option.

 

[Tooloose]

Did you at least chamfer the ports? That's one of the biggest issues they have. Looking forward to your test.

Yes and polished the transfers top to bottom , replaced the crankseals and new gaskets all the way down to the factory oiler and new Boysen reeds and complete carb overhaul. Premium 93 pump non ethanol feul only and the tores system is still fuctional.2 years later now and it's still running knock on wood. Needle and seat needs cleaning due to setting.

 

[Luis_Mcdowell]

Great job, Ken!