Buying one of these this payday

[gary55]

This head may be different from those I have tested, but i highly doubt it. I don't think you will have over 100 lbs. of compression. My guess will be around 90 or less because they are not advertising any material taken from the top of the cylinder. curious to hear your results.

 

[Randall]

This head may be different from those I have tested, but i highly doubt it. I don't think you will have over 100 lbs. of compression. My guess will be around 90 or less because they are not advertising any material taken from the top of the cylinder. curious to hear your results.

Okay.

I'll be measuring it as soon as I get a compression tester on the 1st.

 

[Passenger66]

I know this thread is a bit old, but I had to reply. I recently bought a 66cc kit and after a lot of reading in this forum, I decided to check the compression. With no modifications to the stock head or cylinder I was getting readings at 165psi. I thought my gauge from Matco was defective so I retested with a snap-on compression gauge and got the same results. I was happy to see that other people have also had similar high psi readings from this head because I have tried searching this forum before and found nothing on very high stock head psi readings.
Since then I have replaced the cdi and needle bearings to hopefully prolong the life of my kit. I am looking to get an aftermarket head to reduce compression and get into that 130psi safe zone...well safer zone.

 

[gary55]

I know this thread is a bit old, but I had to reply. I recently bought a 66cc kit and after a lot of reading in this forum, I decided to check the compression. With no modifications to the stock head or cylinder I was getting readings at 165psi. I thought my gauge from Matco was defective so I retested with a snap-on compression gauge and got the same results. I was happy to see that other people have also had similar high psi readings from this head because I have tried searching this forum before and found nothing on very high stock head psi readings.
Since then I have replaced the cdi and needle bearings to hopefully prolong the life of my kit. I am looking to get an aftermarket head to reduce compression and get into that 130psi safe zone...well safer zone.

Seems that there are a lot more variations to these engines coming around lately. Could be that I wasn't looking in to them as far in the past though. The most recent engines I have received have a deck height on the case 1mm closer to the crank weights than the previous engine. They have a 40mm stroke, type B piston, and are using 2 base gaskets to make up for this, and still have 140psi. I imagine if I removed one of the base gaskets it would be around the 165 you are getting. These engines have 8mm engine mounting studs front and rear, and come with a 40mm spacing on the intake studs. Curious if that is what you have but only 1 base gasket was applied when shipped. At any rate the after market head should bring you down to 130/135.

 

[Passenger66]

Until I can get the new head, would it be better to double gasket the head or the base? Assuming only 1 gasket is on each right now

 

[gary55]

Until I can get the new head, would it be better to double gasket the head or the base? Assuming only 1 gasket is on each right now

At the head will drop compression. At the base will drop compression and raise the ports which may weaken low end torque but add top end speed. It's just kinda what you want.

 

[Frankenstein]

In case anyone is interested, don't buy that engine on payday, I've had enough personal experience with that specific product to make this statement competently. There are a few reasons why, and I'd like not not publicly bash a seller, so if you really must know you can ask via private message why.

I will say that all modifications can be done by anyone with a dremel and skills to use it. Having said that it's not particularly worth the price considering the price of an unmodified engine and the amount of time it would take an individual to do the same mods would be minimal (and partially unadvisable)

 

[gary55]

The most recent post, passenger66 is only buying a head. The OP buying the engine did so in sept. 2016. Better windex those goggles.

 

[Frankenstein]

The most recent post, passenger66 is only buying a head. The OP buying the engine did so in sept. 2016. Better windex those goggles.

Yes thanks for reading everything I read and telling me what I read...

I was able to outpace that engine even though I weigh in excess of 100 pounds more than the rider and bike with that motor, this was about 50mph and his was topping out at 46ish. I saw specific flaws in the motor design as to how it was modified, and everything below the belt was stock.

Yes the motor seems to do at least 45 with a 60-70 pound bike and a 130 pound rider upon arrival. This is with reed valves on both motors (not included.) However the price is not worth it, the head is only found used, or directly from the seller, that's fine, I think it's worth what it's sold for. The cylinder mods are done to a 30 dollar cylinder, probably take 20 minutes to cut out, and receives a price hike that seems unreasonable. The lower end had no modifications or upgraded items

 

[gary55]

Yes thanks for reading everything I read and telling me what I read...

I was able to outpace that engine even though I weigh in excess of 100 pounds more than the rider and bike with that motor, this was about 50mph and his was topping out at 46ish. I saw specific flaws in the motor design as to how it was modified, and everything below the belt was stock.

Yes the motor seems to do at least 45 with a 60-70 pound bike and a 130 pound rider upon arrival. This is with reed valves on both motors (not included.) However the price is not worth it, the head is only found used, or directly from the seller, that's fine, I think it's worth what it's sold for. The cylinder mods are done to a 30 dollar cylinder, probably take 20 minutes to cut out, and receives a price hike that seems unreasonable. The lower end had no modifications or upgraded items

Think nothing of it.