JerryHawk250's Lifan KPX250

[Christina Rae]

Originally Posted by Thumper

A dealership? Are they willing to work on the bike? This is definitely a better deal on a great bike compared to the price of the SSR.

no, private sale

[kcdano2022]

Has anyone upgraded the suspension? Is it possible? I have done just about every upgrade I can other then the suspension, the brakes and exhaust.

[JerryHawk250]

Originally Posted by kcdano2022

Has anyone upgraded the suspension? Is it possible? I have done just about every upgrade I can other then the suspension, the brakes and exhaust.

Anything is possible. I find the KPX doesn't really need any mods. All thing i would like to do is fine tune the ECU. I know there's more power available just in tuning.

[Discoveror]

Originally Posted by JerryHawk250

... i would like to do is fine tune the ECU. I know there's more power available just in tuning.

I came across a Good dyno-tuning outfit which meticulously showed (using a wide-band oxygen sensor and meter ... on the dyno) that a Honda Grom ECU made for a near perfect (stoichiometric) 14.7:1 air:fuel ratio ... UNTIL the last 10% of throttle opening where the air:fuel ratio dropped to ~13.2:1 - to make maximum power at wide-open throttle.

So, I ran my 2023 Grom at ~5,000 rpm (NOT wide-open throttle) for awhile, killed the ignition (withOUT closing the throttle), pulled the spark-plug and, sure enough, the plug center insulator was white as snow. Is that what a perfect 14.7:1 air-fuel ratio looks like on the spark plug center insulator?

Today we're Forecast to reach ~50*; I'll try running wide-open throttle - to see if the same approach shows the sought after light TAN plug center insulator, which used to be depicted as 'perfect' on Champion spark plug charts in the back of gas station bays?

[superjocko]

Originally Posted by Discoveror

I came across a Good dyno-tuning outfit which meticulously showed (using a wide-band oxygen sensor and meter ... on the dyno) that a Honda Grom ECU made for a near perfect (stoichiometric) 14.7:1 air:fuel ratio ... UNTIL the last 10% of throttle opening where the air:fuel ratio dropped to ~13.2:1 - to make maximum power at wide-open throttle.

So, I ran my 2023 Grom at ~5,000 rpm (NOT wide-open throttle) for awhile, killed the ignition (withOUT closing the throttle), pulled the spark-plug and, sure enough, the plug center insulator was white as snow. Is that what a perfect 14.7:1 air-fuel ratio looks like on the spark plug center insulator?

Today we're Forecast to reach ~50*; I'll try running wide-open throttle - to see if the same approach shows the sought after light TAN plug center insulator, which used to be depicted as 'perfect' on Champion spark plug charts in the back of gas station bays?

A stoichiometric mixture will leave next to nothing on a plug insulator during a short term plug reading on a new plug. Of course, the plug will color a bit over time even with a stoichiometric mixture as engines do burn some oil that gets past the piston rings under conditions of high engine vacuum (typically deceleration) and also what oil vapor comes through the crankcase breather into the airbox.

If the mixture is in the 13-ish : 1 ratio at WOT, I still wouldn't expect much additional coloration of the plug insulator on a short plug reading run. 13:1 is still fairly lean for a maximum power scenario unless the engine in question is in a relatively mild state of tune mechanically (compression, cam, etc.). Air fuel ratios of 10.5:1 - 12.5:1 are generally considered safer for maximum load conditions on an engine that may be approaching conditions of pre-ignition under high load demand. The additional fueling provides significant cooling that staves off the ill effects of high combustion chamber pressures and temperatures. Of course this comes with a trade off of much higher exhaust emissions of CO and HC. These will ideally mostly be cleaned up after the fact by a catalytic converter but the CAT typically won't tolerate those conditions for an extended period of time without suffering heat-induced degradation. That said, modern metallic substrate CATs do tolerate those conditions much better than ceramic substrates.

[Discoveror]

Originally Posted by superjocko

... If the mixture is in the 13-ish : 1 ratio at WOT, I still wouldn't expect much additional coloration of the plug insulator on a short plug reading run. 13:1 is still fairly lean for a maximum power scenario unless the engine in question is in a relatively mild state of tune mechanically (compression, cam, etc.). Air fuel ratios of 10.5:1 - 12.5:1 are generally considered safer for maximum load conditions on an engine that may be approaching conditions of pre-ignition under high load demand.

Having run a few miles wide-open (in both 4th & 5th gears), cut ignition (withOUT closing the throttle), pulled the spark plug and examined the plug insulator, it would take a vivid imagination to detect a color difference.
vs. part-throttle at 5,000 rpm
My vivid imagination detected VERY slight greyish coloring vs. the snow-white insulator at 5,000 rpm partial throttle.

This Grom engine is a 'mild tune' ... SOHC, 2-valves, 10:1 compression, running 87 octane. At wide-open throttle for miles, the instrument panel indicated 102 mpg, btw ... ` gotta make ya smile! ... even though it'll only transport you at 45 - 50 mph, sitting straight up (no tuck) on a flat road sans much wind; ` amazing what 8.7 hp to the wheel (per dyno) will do for ya !

Why point out this non-China-bike example? I did so as an illustration of what spark plug insulators might look like, managed by a current ECU injection system.

[JerryHawk250]

I updated the ECU today. Man, what a difference. It definitely idles much smoother and the throttle is much more responsive. Much better low-end power for sure.

[2LZ]

Glad to hear the reflash was a success, Jerry! BTW, where did you rent that handsome stunt-double for the vid? You did an amazing voice-over! Could hardly tell it wasn't you!

[jsumd]

Originally Posted by JerryHawk250

I updated the ECU today. Man, what a difference. It definitely idles much smoother and the throttle is much more responsive. Much better low-end power for sure.

Glad you got some good results from it!

[JerryHawk250]

Originally Posted by 2LZ

Glad to hear the reflash was a success, Jerry! BTW, where did you rent that handsome stunt-double for the vid? You did an amazing voice-over! Could hardly tell it wasn't you!

With AI and a good wireless mic, you can make anybody look good.

[thedakotakid]

Any idea if the new bikes being shipped by Venom have the ECU's flashed already or do you need to send it in?

[TitusvilleRmiles]

Hey Jerry, Nice information and I have the KPX 250 as well. I have looked through the thread and the web and have what sounds like the infamous engine noise at acceleration ping, rattle. I really think it might be cam chain noise. Lifan made it almost impossible to access the cam chain tensioner by using a phillips instead of a bolt to get to the tensioner. You can't even back out the 8mm bolts on the sides of the tensioner because the starter is in the way. So now it is more like to get the starter out to the way you have to remove the exhaust pipe, starter, and then tensioner. I custom made a shorty phillips screwdriver and with vice grips to try and loosen it up but no-go. Lifan has not engineered this task of access to the cam chain tensioner easy at all.

[TitusvilleRmiles]

cam chain tensioner

[TitusvilleRmiles]

I have been waiting now 3 weeks for them to send me the programmer. I have emailed them yesterday for the third time. The second time I emailed them a week ago they said it was "not ready". I am not sure just how good this service is right about now. I would send it in if I could get this done faster. The hesitation in throttle response is annoying. I have had a dozen bikes and not my first rodeo.

[thedakotakid]

It's 2024, is the KPX 250 still the 'best' for the price? Any news of a newer model coming out this summer? I am tempted to pull the trigger at the current price (2800, give or take).