GX390 tuning w/OEM rod & flywheel

C

centurion

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How much tuning is "safe" with OEM rod and flywheel. ?
 

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Generally if you were to go over 6000 rpm it is advisable to install a billet aluminum or PVL flywheel. An aluminum billet rod would also be needed. Since the GX390 makes most of its torque in the low rpm ranges, for that kart you might want to keep the rpm range below 6000.

Installing a performance exhaust pipe and air filter plus adding a few teeth to the rear gear would be a good starting point for increased power and acceleration.
 
Compu-kart said:
Generally if you were to go over 6000 rpm it is advisable to install a billet aluminum or PVL flywheel. An aluminum billet rod would also be needed. Since the GX390 makes most of its torque in the low rpm ranges, for that kart you might want to keep the rpm range below 6000.

Installing a performance exhaust pipe and air filter plus adding a few teeth to the rear gear would be a good starting point for increased power and acceleration.
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Thanks, I might go for the NR racing's Hop Up Kit - Stage 2.
I do not want to tune so much that I have to buy a expensive unreliable clutch etc., then it might be cheaper and more reliable with a rotax max kart :)
Have a Noram 1: 2 wet clutch, and do not know how much more power it can handle.
Read that some was having problems with manual starting w/ billet flywheel's too.
 
I doubt that any amount of add-on parts will be a problem for that clutch. When you start boring the cylinder, increasing the compression ratio, porting the head, etc then we can revisit the clutch situation.

As far as the comparison between a big block and a Rotax, I have years of experience building and road racing both. Without doubt, and by the greatest superlative in the English language the Rotax is the king of reliability, ease of maintenance and greatest interval between rebuilds between the two.

I've built plenty of engines with a billet flywheel, hard starting vs stock flywheel is news to me. Others may chime in on that issue.
 
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