Simple Zenoah Tuning

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Dreadnought

Well-Known Member
Messages
50
I've got a feeling that I'm going to regret this, but:

I'm looking for some basic help on tuning up a Zenoah G230:

FIrstly what squish clearance should I aim for and is this best achieved by removing the the base gasket or machining the flange on the head / barrel?

Inlet port, very roughly is it better to raise or lower it and by how much?

Same question for the exhaust port?

Is it worth matching the piston skirt to the inlet port and are any other modifications required?

Inlet, does increasing the length help, or would aftermarket reed valves be better?

Finally, carb, would a 990 be best or something else?

I'm not looking to go to the wild side of tuning just get the standard motor to a good state with minimal work.

Cheers
 
I've got a feeling that I'm going to regret this, but:

I'm looking for some basic help on tuning up a Zenoah G230:

FIrstly what squish clearance should I aim for and is this best achieved by removing the the base gasket or machining the flange on the head / barrel?

Inlet port, very roughly is it better to raise or lower it and by how much?

Same question for the exhaust port?

Is it worth matching the piston skirt to the inlet port and are any other modifications required?

Inlet, does increasing the length help, or would aftermarket reed valves be better?

Finally, carb, would a 990 be best or something else?

I'm not looking to go to the wild side of tuning just get the standard motor to a good state with minimal work.

Cheers

Not sure if you want to go that far on a 23 cc engine ,I don't think it is worth it!... :unsure:
 
You just opened a can of worms mate. Squish should be 0.018-.020" normally a base gasket delete will get you close. If your new to porting you wont want to be changing your port numbers at first. Just widening and blending them for better flow. You can clean up the transfers and the transfer covers as well. However much you take from the base you could raise the ports as well. This would get you closer to base port timing. Raising the exhaust port will give you better top end at the trade off of bottom end torque. Of you search engine porting, I have several links spread out through the forum, as well as my dbxl build where I showed most of a mild port job being done. As the engine is timed by the piston you wont want to mess with it right away. Raising the intake skirt has much the same effect as cutting the skirt down. Where cutting a relief in the top of the piston on the exhaust side will yield similar results as raising the exhaust port. Theres an amount that you can go with wise in the ports and stay in the safe range, I cant remember it off the top of my head. Plan on messing up a few top ends before you get it to perform how you would like it to. Normally I suggest getting an old cylinder from a small engine shop to try playing with before going all in on something you want to use. Good luck lol.
 
You just opened a can of worms mate. Squish should be 0.018-.020" normally a base gasket delete will get you close. If your new to porting you wont want to be changing your port numbers at first. Just widening and blending them for better flow. You can clean up the transfers and the transfer covers as well. However much you take from the base you could raise the ports as well. This would get you closer to base port timing. Raising the exhaust port will give you better top end at the trade off of bottom end torque. Of you search engine porting, I have several links spread out through the forum, as well as my dbxl build where I showed most of a mild port job being done. As the engine is timed by the piston you wont want to mess with it right away. Raising the intake skirt has much the same effect as cutting the skirt down. Where cutting a relief in the top of the piston on the exhaust side will yield similar results as raising the exhaust port. Theres an amount that you can go with wise in the ports and stay in the safe range, I cant remember it off the top of my head. Plan on messing up a few top ends before you get it to perform how you would like it to. Normally I suggest getting an old cylinder from a small engine shop to try playing with before going all in on something you want to use. Good luck lol.
Thanks for this, I'm used to messing about with Yamaha YPVS motors and with some simple squish adjustment, cleaning the transfers and ports I was getting some decent benefits over the factory motor, even more so when I fitted a programable YPVS controller. As you may have guessed I also have an old G230 to play with and to be honest I just want to have a go more than set the world alight. Being able to understand where the restrictions in these motors are and to push them a little bit also fills the evenings when I'm not out training. Thus I'm after a good base setting that I can try different filters, carbs, inlet lengths, pipes etc to keep me away from the fridge and TV over the winter months.

I'm looking at making a simple plate to mount the motor and tank on in a vice so I can measure rpm changes to develop a good combination.

Its only a bit of fun.
 
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