CR topend rebuild time

[Durt Cycler]

:uh: Well it's winter time and I tore my topend off this week and found out everything was in great condition tho the powervavles and guide were carboned up im guessing from the previous owner running Honda HP2. Cylinder is std. plated bore with OEM piston in it. Bike had about 200HRS+ on the topend I'n guessing ( about 50 from me and the previous owner had the bike for a year ). Bike had about 125PSI of compression but my compression tester isn't accurate cause some air does leak out of the plug hole but 125PSI with a leak sounds good. First off the cylinder head looks brand new to the naked eye but up close with a magnifying glass you can see very small nicks most likely from low octane gas but has no visible marks on it. Powervavles need cleaning also. Cylinder bore looks perfect, no scratches at all in the plating, you can still see most of the cross hatch pattern in there. Piston looked great, no scratches in the piston, piston top looked like this:

But I noticed some but not alot of blowby near the ring area and the end of the ring were worn. Under the piston I found a hot spot:

So from what it is saying the first picture says my bike is jetted correctly but the hot spot means it was running lean ( i know my water pump is working )? I have had some jetting problems lately with it but I am running a 170 main (172 stock) 55 pilot (58 stock) N1470S (N1469S stock). Should I worry about this before I put my new Wiseco topend in it? Thanks for any help :uh:

BTW: it has FMF Fatty pipe, FMF says to run a 58 pilot so i switched to it and a N1468S needle which my bike has 2 sizes bigger.Boyesen Power Reeds also which say to go 1-3 down on the main. I put my clip in the 2nd position from 3rd so maybe that will help.

 

[Adrenaline]

I always thought a black spot underneath was fuel leaking under the piston then attatching itself and exploding from the heat. Thats what i've always been told. It can cause a nice hole in your piston though!
125psi isn't bad how about a little under 100psi without a leaky tester? try that for size lol. Change that there piston before 70 hours comes around next time youngin your a lucky soul indeed! :cool:
The best way to jet a bike and get proper readings is to do it this way
-Go to your local store and buy a handful of BR8EV plugs
-Switch your plug out and then start the bike up and keep it running in the pilot circuit only! when enough time has passed for the plug to turn it's color kill the engine and change the pilot acording to whats needed. Tan plug don't mess with it, black go to smaller pilot, whitish go larger pilot if not u'll have a toasted piston if ya will :eek:
-Repeat the steps and slowly go to each of the different circuits this will dial the bike really close to what you'll need. You may need to raise or drop the clip and turn the airscrew a little to fine tune it but it will but you on the mark. Hope I helped;)
ADR

 

[NO HAND]

Originally posted by Adrenaline
-Switch your plug out and then start the bike up and keep it running in the pilot circuit only! when enough time has passed for the plug to turn it's color kill the engine and change the pilot acording to whats needed.

I think that the plug reading method will be an indicator of your jetting only in the high speed circuit(main jet). For the low speed circuit, the quickest way is probably the ride and feel method. Remember that the pilot is affecting mainly from closed to 1/4 throttle.

 

[Rich Rohrich]

Originally posted by Adrenaline
The best way to jet a bike and get proper readings is to do it this way
-Go to your local store and buy a handful of BR8EV plugs
-Switch your plug out and then start the bike up and keep it running in the pilot circuit only! when enough time has passed for the plug to turn it's color kill the engine and change the pilot acording to whats needed. Tan plug don't mess with it, black go to smaller pilot, whitish go larger pilot if not u'll have a toasted piston if ya will :eek:
-Repeat the steps and slowly go to each of the different circuits this will dial the bike really close to what you'll need. You may need to raise or drop the clip and turn the airscrew a little to fine tune it but it will but you on the mark.

Sorry but that won't work. Plug readings are useful for jetting the main, determining plug heat range, verifying ignition timing, and spotting detonation, but you'll never be able to accurately read the mixture strength of the low speed circuits .

The following links should get you the info you need on jetting:

http://justkdx.dirtrider.net/carbtuning.html
http://justkdx.dirtrider.net/jetneedles.html
http://www.ericgorr.com/techarticles/carbtuning.html
http://www.ericgorr.com/techarticles/sparkplugs.html

 

[Adrenaline]

darn!!! I thought i had something! well thanks for posting the links so I can become a brighter one!!!