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Project Clapped out 1998 KX250... What works? Turbo Crank?
Posted: Tue Feb 13, 2018 12:39 am
by Sandblaster
Jason has had this bike kicking around for a lot of years...
In 1998 this was the bike of the year.
It is well worn and the top end is completely clapped out.
I've always focused on the KX500's but we are going to see what we can do on this KX250...
Before we do anything it is getting the air cleaner cleaned up, fresh fuel and oil, new plug, and a street tire on it.
Then it is headed to the dyno so we can have a good laugh at it..
- 1998 KX250 KX Guru build 101.jpg (563.2 KiB) Viewed 8952 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Tue Feb 13, 2018 1:18 am
by Sandblaster
Beautiful....
- 1998 KX250 KX Guru build 102.jpg (214.76 KiB) Viewed 8950 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Tue Feb 13, 2018 11:10 pm
by Sandblaster
The bike started on the second kick..
Amazing that it sat for 5 years in such rough condition and started right up..
After the clean up and start up, Jason decided that he wanted to use a different wheel and tire for the build...
I guess he was concerned about the extra weight..
After installing the tire he discovered that the bearings were junk.
I just happened to have some new mid 90's Yamaha YZ bearings which fit perfectly..
But, he will have to re-use his seals because the YZ seals are a larger diameter then the Kawi seals..
Just for grins I looked up the Rear Wheel HP for the 2018 KTM 250 SX and it was a blistering 37.8 hp.
I thought it would be more... but whatever.
I'm sure that when we are done we will be a bit above that number
- KX250 DYNO REAR WHEEL.jpg (254.01 KiB) Viewed 8947 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Wed Feb 14, 2018 2:06 am
by Sandblaster
Ok... The tire is on and we are ready for our first dyno run...
- 1998 KX250 KX Guru build 103.jpg (593.33 KiB) Viewed 8945 times
- 1998 KX250 KX Guru build 104.jpg (599.44 KiB) Viewed 8945 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Thu Feb 15, 2018 2:44 am
by Sandblaster
What I haven't shown is all the bottom end bearings, seals, gaskets, ect that I ordered for this project.
Today I received the last piece..
Gotta love those Wossner products
So now.. the balls in Jason's court to get get this thing dyno'd and start the tear down..
- 20180214_161734.jpg (244.63 KiB) Viewed 8943 times
- 20180214_161750.jpg (432.31 KiB) Viewed 8943 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Wed Feb 21, 2018 4:10 am
by Sandblaster
Today we took the bike to a local shop to get some base line dyno numbers:
- 20180220_132433.jpg (314.91 KiB) Viewed 8930 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Tue Feb 27, 2018 1:42 am
by Sandblaster
Re: Project Clapped out 1998 KX250... what works?
Posted: Sat Mar 17, 2018 8:40 pm
by Sandblaster
Well... we are a step closer to dyno results.. Steve Parris just finished cutting the crank webs...
- received_2069627899730957.jpeg (287.67 KiB) Viewed 8801 times
Re: Project Clapped out 1998 KX250... what works?
Posted: Sat Mar 17, 2018 8:52 pm
by 60something
What's the purpose of the cuts in the crank ?
Re: Project Clapped out 1998 KX250... what works?
Posted: Sat Mar 17, 2018 11:07 pm
by Sandblaster
The original idea was to push more of the charge up the transfers.
What those guys found out was that there was only so much charge in the lower end and sweeping it up the transfers did not produce more charge.
In fact, a lot of guys gained a little bottom end but lost a lot of top end most likely due to increased turbulance.
The idea behind this design is to compress the charge, then send it up the transfers.
Steve Parris has a patent on this design.
According to Steve he is getting about 7 HP gain with a KX250.
So, we shall see what the dyno says.
I'm very excited.
If we can get 4-5 HP I'll be thrilled.
