I bought the FL250 with a running motor (( Internal Combustion Engine ? )) ((Internal Combustion Engine?)), but it needed a complete overhaul. The crank seal behind the stator was completely toast so my guess is the Engine leaned out or even ran away. The Engine would not hold any pressure at all as any pressure I gave it blew straight out the failed seal. The Engine suffered a catastrophy by way of the piston chunking and the top piston ring actually went missing destroying the head in the process. I I had really known this I would not have gotten this FL250, but it did have 115psi compression and did run with a half blown piston though not very well.

I know the original Engine failure was due to a failed crank seal. Now; the Engine has a completely rebuilt bottom and top end with new crank main bearings. The crank itself was fine with no play but every other moving and sealing part was replaced. The cyl was honed 0.25mm over and a doner cyl head was used in the rebuild. The Engine is now holding a pressure test and has 135~140 compression with about 1 hour on it.

The stock fuel pump was rebuilt, as was the carb. New filter also.


OK so I was able to get a bit of tuning happening and notice the following things:
1. I believe I set my points/timing incorrectly as the Engine is very sluggish. Timing is likely retarded a LOT, but that's OK atm because it may be easing the motor (( Internal Combustion Engine ? )) ((Internal Combustion Engine?)) and resisting some ping/detonation in case of fueling problems.
2. 125 main jet and the kart is bogged down. I don't have a 115, but a 110 main causes a bit of top-end ping which is dangerous. (I LET OFF FAST! after the first TING)
3. I went with a 120 main, and the Engine will get to about 7,000 rpm as indicated on my tiny tach, but after about 5~10 seconds the RPMs will drop and the Engine starts to ping slightly (I LET OFF FAST! after the first TING)
4. So I believe there is a fuel delivery problem even though the pump was rebuilt.
5. If I ride around at about 2/3 throttle the Engine will eventually start to slow up and get very lazy (No pings). If I then let off for about 10 seconds the power will be restored. This is highly indicative of a fuel delivery problem as well.
6. I'm using a stock/Honda fuel restrictor T fitting and its all installed correctly.

My guess is this fuel pump just doesn't have the guts to keep up with the demand. Next time I start the kart I'm going to take a mid throttle measurement of how much fuel is delivered by way of the fuel pump over ~10 seconds. I don't want to convert the delivery system to gravity feed as my stock fuel tank looks to be in good shape.

Thank you

The cart still wasn't running totally right with the new pump from what I could tell-but I did find another problem. The intake boot between the carb and Engine had two slits in it likely from a recent backfire. I can't believe how much they cost, but in the meantime I was able to reinforce with an outer layer of tightly fitted rubber heater hose so it won't leak for now. I found this leak when spraying carb cleaner stalled the Engine.

Hopefully that will help as well.

The plug looks OK but by now its pretty dark from oil.

What chemical works best for cutting 2-stroke crud sludge?

Did you end up cooking/whacking/blowcleaning your exhaust out???

I found a large piece of exhaust wrap lodged and stuck inside the pipe which was causing poor slow performance. It must have been blocking a ton of exhaust flow. The Engine is running a lot better now but I still think it may need a leaner needle and maybe a 115 or 117 main jet. I'll have to do some plug chops fir sure tho.

Also my timing may still be retarded so I'll figure that out too.

Thank you.