02 cr 125 is fast

[steve125]

I have my base set up for the 02 cr125.....carby....350-360m..std00yz125needle..3rd clip...25..pilot...1.5..as....(for colder weather 60-50.....30..pilot...same needle but 1 richer straight section)....reeds..delta 2...with opened and matching manifold......cylinder....tighten piston to cylinder clearance with a wiesco piston....1.5 thou....std is 2.5 thou....very noisy! stock.......port timing is quite advanced so the only changes at this time......lower cylinder .010 for more compression and tighter squish ( 200 psi pvs open..... .85mm squish measured)........pipe....for best short course.....00 pc pipe and short silencer (you must use 02 silencers to fit subframe correctly).....long course or prefer top end power is the 02 pc pipe...long or short sliencer.....gearing..13..52 dry course......13..53....lots of traction.......Oh and the pv mod spacer of 7mm diameter.......with these mods you can pick the power you like and it's a huge improvement over stock!!!!!!!...... I prefer the mini 250 feel of the 00 pc pipe....its a good compliment to the delta that helps top..........right now with these mods the bike just rips!!!!!!......now with this base we will go with the 2mm over for even more......:cool:

 

[EricGorr]

Thanks for the update Steve! I've done some experiments with the new exhaust manifold. For the rest of you guys, the 02 exhaust manifold is still a D-shape but it has less cross-sectional area and is 15mm longer which should improve the low end power. I've installed and modified the exhaust port for a 01 manifold to give the 02 model more top end. The 02 manifold fits the 2000 & 01 models and gives better low end.
Overall the 02 cylinder has more advanced port timing, similar to what we run on karts or for expert outdoor mx riders. Most riders could benefit from retarding the port timing by turning down the cylinder base .75mm and reconfiguring the head.
Happy tuning!
Eric

 

[Jman271]

A few questions for Steve 125 and E Gorr,,,

Hello, new member here, and 02 CR 125 owner. I have a few quick questions,,,
(1) Steve, is the 00 yz needle the 9-71? If so, does it require a diff nozzle? I ran an 9-71 needle w/a S-8 nozzle that helped out on my 01 CR. I know they changed the nozzle system this year, that's why.
(2) The pv spacer-I've heard of it, but never used it. Can I make one? How is it installed, and what does it help?
(3) Re-configuring the head to the stock squish band/ clearnace and angle? How much squish clearance should there be, stock? Thanks allot for your input, I will be posting back quite a bit on this site regarding tuning etc,,,. I bought porting tools recently, and I am looking into all aspects of engine design and tuning. I also will be buying a lathe, granite measuring plate, cc gauge, etc. Thanks allot, TTYL-Jman271

 

[gainsboro]

id like to know about this elusive 7mm spacer thingy !
what is it
what does it do
where does it fit
where do i get one
or can i make one out of a sqeezy bottle top ?
thanks

 

[marcusgunby]

The spacer is a 7mm o/d dia pin that fits over the std stopper on the powervalve.It alters the blow down timing for more bottom end power.You can make one very easily-not out of a bottle top though:D

 

[steve125]

Ok, the 02 Honda carb is the same as the 00yz125. All parts interchange but on the 01cr carb only the main and pilot jets will work. Now that it's getting colder the stock 02cr needle should work ok,the difference with the yz needle is small only in the tip taper and the straight section is slightly leaner. Starting in 2000 the cr125 changed it's power valve, the problem is it's over rotated and does not allow for enough blow down timing. For the 01 and 02 models Honda drilled 2 small holes in the corners of the valves to help but it wasn't enough. The valves can be ground up in profile or a small spacer can be put over the power valve stop pin on the side of the cylinder. We made a bushing that has a diameter of 7mm and this opens the pv's an additional 3mm when closed. The idea is to let the engine have more time to clear it's exhaust before the transfers open. As far as the squish clearance stock is very close to what is the norm at around 1mm for 125's.

 

[Jman271]

OK, so if I get you correctly, I can make a bushing that fits over the pv stopper tab, that is 7mm in dia? This will actually prevent the pv from closing all the way like it did stock, correct? SO, how does it stay on that tab? Does it need to be drilled and fit w/a pin to hold it on, or good old fashioned, inter-fearance fit? ALso, I don't have my digi-calipers in hand, but what it the translation from 1mm to thousands? Thanks for you help, I'll post back some set up tips that have worked for me in the NE area 0-1000 asl, and all kinds of horrible weather conditions. Steve, do you have a web-site or something? TTYL-Jman271

 

[marcusgunby]

It needs to be an interferance fit as it takes quite a bashing.45 thous to a mm i beleive.

 

[Jman271]

??? 45 thous- a mm? Please explain,,,,

 

[cp380sx]

.03937" = 1mm

 

[marcusgunby]

Its been a while since i slept properly.

 

[NO HAND]

Originally posted by marcusgunby
It needs to be an interferance fit as it takes quite a bashing.45 thous to a mm i beleive.

Would you recommend using also an adhesive to keep it in place or the interference fit is enough?

 

[marcusgunby]

cant do any harm to add some adhesive as well:)

 

[Jman271]

BTW, what sort of material has worked well for this, SS?

 

[NC514]

My Cr 125 is fast!!!

mine ripps, Where can i buy one of those power valve stop bushing's? can i just wrap duct tape around the peg stopper? LOL!!! J/k!:eek:

 

[marcusgunby]

I doesnt have to be as hard as SS.I just found a bit of tubing of the right OD and whacked it on.If it wears 0.5mm in 2 years im not sure i would notice.As long as its secure.Eric Gorrs book goes into detail on the 2000Cr range and alot of it still applies-Eric is the check in the post?:D

 

[Jman271]

Hey Eric/Steve125???

If the base is turned down .75mm which is roughly .029, how much would come off the squish to maintain enough squich clearnace, .029? Or is the stock clearance to big? Would taking the squish down .010, while maintaining the stock angle of the squish, keep tighter toleances and have any benifit? Thanks for your help-

 

[mintc1]

i have a 2001 cr125 will the pv spacer work the same on it ? does it hurt the top end or mid -range power?

 

[marcusgunby]

The 01/02 have similar or identical powervalves so the mods listed will work on both as far as powervalve mods go.On the squish clearance-the 01/02 has a very tight clearance from Honda and unless you run very good fuel it would be wise to keep it the same.Even std its important to run as good a fuel as is affordable.In the UK i run super plus unleaded.If i run on std unleaded i chase jetting around all day.I can tell you that jetting can run fast when im after it:confused:

 

[mintc1]

i run 113 octane fuel is this enough to do this mod? Would brass be hard enough to make this spacer out of?

 

[marcusgunby]

Brass would do the job.I would think with 113octane you may be able to close the squish down to 1mm.On the dyno i think ive proved that a 3degree squish band removes a big dip at 8000rpm that was apparent when we ran the std parrallel squish.Im not 100% sure it was this mod but it certanly seemed better after the head was modified.3 degree sqiush 7mm wide with a clearance of 1.1mm and 1cc more volume to run on superplus unleaded.For race gas i dont know.