What year cylinder is best for CR125???

[Jman271]

In regards to 00 and up,,,what jug would be the best for modification for an 02 CR125? I know a few years back, Yamaha was running 94 250 jugs on their 250 race bikes, same priciple here. I would think that if you went w/ an earlier year cylinder, you would have to get the ignition system too, no? Reason being, I have a new 00 CR125 "B" jug that I can either sell, or use. I think I remember reading somewhere that the 00 jug was best for low end, and that top was easier to get modification wise than low end. What do you guys think,,,,let the bashing begin :aj: :aj: :aj:

 

[marcusgunby]

I dont go for all this swapping year cylinders-if you all ready have a 00 then it would be worth a try to run it.The cylinder porting on any recent Crs isnt bad so you wont gain alot by trying cylinders.
Me and steve125 have done extensive testing on the 02 crs-probably more than most race teams-heres what we found
v force on low setting gives over 1hp more
ignitions need to be replaced-i use a wulf-steve has a PC-another 1hp gain.
exhaust i use FMF SST, steve runs a DEP-both give around 1hp more on top end.
Lowereing the cylinder(to make it like a 00) gives a tiny bit of bottom but losses more top than its worth.
38mm carb helps top end but we are running 36mm std carbs.
Most other mods do nothing or very little-dont beleive what the mags say-they must have a deal with Honda to sell all the old cylinders.

 

[Jman271]

Thanks Marcus!!!!

 

[steve125]

Marcus lets not forget a good piston to quiet the stock rattle! I use a Wiseco with the std boost window and Marcus runs a Vertex with no window. Mine is set up with a piston to cylinder clearance at .0015. As a side note i compared a SRS racing piston to the Wiseco and found a few differences. The Wiseco is the lightest by 15 grams, the SRS weights the same as a stock piston The SRS has a little longer piston skirt by about 4mm. The SRS has no intake window and no pre drilled holes for the exhaust bridge or the piston pin. It does though have a molybdenum bisulfite coating and the Wiseco does not. The weight seems to be a big issue here between the two, 15 grams is alot, it is very noticeable in holding one piston compared to the other.

 

[marcusgunby]

Steve is correct of course:)i had completely forgot about the piston problems-i assumed everyone had changed theirs to something else:)I also forgot about the skirt being longer on the SRS-my brain is frazzled.

 

[SiCnTwIsTdYz]

u heard the 95 cr125 engines were the best around last year in motocross action scott sheaks mechanioc, takes a brand new cr125 and tears it down, splits the cases and matches them, and than takes the originall cylinder off and puts a 95 on it, i also hears that the 95's were the fastest years out of the cr125's, donmt get me wrong you can too make a cr125 fast but in stock form they are a little "underpowered"

 

[bclapham]

It never seases to amaze me the influence MXA has on the dirtbike buying public! i bet they have moved more units than ricky travis or MC put together, half the bikes in socal are kitted out exactly witht the parts they endorse! (does riding a yamaha make me a hypocrite?).

the more i look into the porting issues, it appears to me that the porting of a cyclinder does not generally make power but rather moves it from one point to another! so if you take a cyclinder from one year i would expext the removal or addition of material to the ports etc can quickly make the same power characteristics as a different year. but would this be good for everyone? surely not, i would bet most people would be much faster if they had their power characteristics suited to their riding style and conditions and not those of MXA.

now ive got that off my chest, i am going to set the jetting and clickers on my bike to the settings MXA tells me, no wonder i am so slow!:)