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General => General Discussion => Topic started by: zephyrprime on August 02, 2019, 03:11:12 PM

Title: K-pipe jetting and a new air intake
Post by: zephyrprime on August 02, 2019, 03:11:12 PM

Hello all.  I was wondering if anyone had messed around with k-pipe jetting and/or using a high flow air intake?

I was messing around with my 49cc Tomos moped recently and I was surprised at what a huge different a new air intake, exhaust, and jetting made on the system.  It's such a small engine that I didn't think it would need much in the way of air flow and exhaust flow.  It has a stock #55 main jet but with the new air intake and exhaust, I couldn't even get it past 15mph with a #58 jet because the mixture was too lean!  I had to jump to a #62 jet to even get it to go to second gear.  From reading some forums, I think it will need a 64 or higher jet which I unfortunately do not have yet.  I have read that the Tomos can increase in speed and power by going to a #58 get even with the stock equipment.

I was thinking that the K-Pipe may be under jetted as well in order to limit its speed and increase its fuel economy.  It's odd that the k-pipe engine is so low revving and low power despite being a small displacement engine.  Other similar 2 valve engines like the Honda CB125r get 14hp at 10000rpm while the k-pipe only gets 8 at 7000rpm.  I think this low level of performance is an indicator that something is restricted on these bikes and I would like to remove those limitations.

I was wondering if any of you had messed around to jetting and/or air intake changes?  What are your opinions on the stock air intake?

Title: Re: K-pipe jetting and a new air intake
Post by: souzamoto on August 02, 2019, 04:19:46 PM

Is your Tomos a 2-Stroke? If so, that's why the K-Pipe seems low reving.
The K-pipe, which I assume is a 125cc, has the emission systems required for the USA/California. Its a bit lean to meet those requirements. You can install a free flowing filter or eliminate the airbox and go with a pod filter. The later you will have to re-jet more aggressively that the prior. Up on the pilot a size or two, up on the main a size or two and adjust the jet needle height in the slide. You will also have to re-adjust the fuel/air screw for the best idle, off idle and decell.
have fun!
CJS

Title: Re: K-pipe jetting and a new air intake
Post by: nikkke on September 19, 2020, 09:18:58 AM

Watch this: https://www.youtube.com/watch?v=6fJA8QklOxU&t=42s (https://www.youtube.com/watch?v=6fJA8QklOxU&t=42s)