Jump to content
Sign in to follow this  

not what i had hoped for...

Recommended Posts

Yesterday was my first chance to really ride my 08 kx 250f that I have been wrenching on for the last two weeks. Motor was a total loss when I picked it up from previous owner, who had dropped 2nd gear and destroyed bottom end. I started with 2 fresh cases and another tranny, a cylinder works +3mm jug, and a slightly dinged head. Added a lightly used OEM crank, JE high comp. Piston, and had the head repaired then ported, kibblewhite +1mm valves all through it, new cam chain, and plenty of high hopes. Bike seems to rev out way too quick, (maybe due to heavier valve train components) and doesn't seem to have much more pop than my 08 rmz250. I didn't go with cams because it seems from the forums here that the 08 cams were decent. Bike also has a pro circuit to full system, any one have any thoughts on this? I guess I just expected more

Share this post


Link to post
Share on other sites

Who did the porting (not bad mouthing - genuine question), do you know anything about it (flow numbers etc)

For a big bore, the ports can be bigger even if they dont flow much more, and the carb bored +2mm can really help.

The 08 responds well to cams, I actually just had a customer ask me if I knew anyone who wanted PC cams for an 08 - no idea how much he wants...but throwing that out there.

With larger valves, were the seat profiles altered to suit? If not - your killing your flow. Everything needs to be redesigned to suit that bigger valve - including the port.

How is the jetting? I'd secure a dyno and see where you are at - will save you tons of time and money in testing things that dont work - when you can spend a half hour on a dyno - get your jetting dialed, and try a few things to figure what's not right.

Share this post


Link to post
Share on other sites

dont know about the flow numbers but i can get them, they wouldnt cut the seats or do the seat profiles until they got the valves in the shop, so they were probably set up correctly. jetting was next on the the check list, i may be in the market for cams, so if you speak to that person who has them, PM me the price and we will go from there, thanks for the input.

Share this post


Link to post
Share on other sites

dont sound right...my 07 with a JE high comp and a freshly rebuilt head with slight porting (I mean SLIGHT) feels stronger than any other 250F I have rode, and other people have rode my bike and are highly impressed (also running team green jetting which made a HUGE difference)

Share this post


Link to post
Share on other sites

For the big bore - they wont apply very well.

You really need to secure a dyno - and stick in an a/f meter.

This truly will save you time and money in the long run - many places are well under 100 bucks an hour - it will maybe take you 30 minutes to dial in almost perfectly.

Considering what you have invested into it at this point - its pretty cheap.

Share this post


Link to post
Share on other sites

Don't know anything about dyno's can it help me dial in my jetting? And, should I hold off until after I have added the pc cams?

Share this post


Link to post
Share on other sites

If the place you are going to dyno cant help you, something is wrong!

But -stick an air fuel meter it in it (dyno place should have it) and it should be right around 12:1 for a baseline. If it's higher than 12:1 (say 13:1 or 14:1) go richer. if lower go leaner...

After that you can spend a lot of time getting it better bases on hp numbers...but that should get you close

Share this post


Link to post
Share on other sites
Don't know anything about dyno's can it help me dial in my jetting? And, should I hold off until after I have added the pc cams?

Usually you would haver to jet down (leaner) because of the bigger engine drawing a bigger vacuum and pulling more fuel through the same size jet.

An engine running rich would fit your description, not revving out, lacking punch and crispness.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...