cr 85 upgrades


16 replies to this topic
  • Moparluvr

Posted August 03, 2010 - 01:18 PM

#1

hi. My son has a 04 cr85. I was wondering if it is worth it to change the reeds to aftermarket? And pipe, already have the r 302 shorty on it.I was looking into the boyesen reeds. I was also considering getting a whole new assembly like the v force 3 or Rad valve. It just seems underpowerd until it hits the powerband in the higher r's. I live in Michigan also. Anyone out there in a similar climate with some jetting specs would be good.
Thanks......

  • mx-4-2

Posted August 03, 2010 - 04:15 PM

#2

hi. My son has a 04 cr85. I was wondering if it is worth it to change the reeds to aftermarket? And pipe, already have the r 302 shorty on it.I was looking into the boyesen reeds. I was also considering getting a whole new assembly like the v force 3 or Rad valve. It just seems underpowerd until it hits the powerband in the higher r's. I live in Michigan also. Anyone out there in a similar climate with some jetting specs would be good.
Thanks......


I have modified my son's '06 CR85RB significantly. When we bought the bike, it was bone stock and only a few hours of time on it. As you note, they don't have much bottom end.

Changing the pipe and muffler made the most significant change. We are running the FMF factory fatty (non plated pipe) and shorty exhaust. The lower end was stronger and much more linear as it revs up in the power band.

We changed the piston to a forged Wiseco and it has a little more compression. This also helped the bottom end.

After these changes, we went to the V3 V-force reeds and did not see any noticable performance improvement. The '06's came rich as stock and so with the mods, we are running the stock #142 main jet and it is still a tad rich.

We also changed the rear sprocket and added a tooth to a 56. The suspension was resprung and revalved to fit my son (130lbs) and that has helped the handling. The cumulative motor mods made a significant difference.

Good luck with yours. As a Honda guy, it's great to see a CR on the line in the 85 class as there are so few still being raced.

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  • Moparluvr

Posted August 03, 2010 - 04:33 PM

#3

Thanks for the input. I will go with a pipe first then. Which pilot jet are you running? Do you know the clip position ?

I am trying to keep this 85 in his interest as he rode with some Rm 85's this weekend and keeps talking about them. I will admit the Rm's did sound alot throatier and I asked one of the dads and he said it was all stock....

  • gruberyz

Posted August 03, 2010 - 04:46 PM

#4

My son ran an 05 CR85RB in MX and cross country. He won the 85cc XC championship on it and finished third in sportsman class racing against 125's through 450's if your CR85 is not feeling fast I wonder if it's being ridden right. I did do dual stage reeds and FMF pipe and muffler which actually took a little off the bottom. In my opinion best thing you can do on CR85 is stock pile clutch components so as they are destroyed staying on the pipe you can keep it in top shape.

  • mx-4-2

Posted August 03, 2010 - 06:17 PM

#5

Thanks for the input. I will go with a pipe first then. Which pilot jet are you running? Do you know the clip position ?

I am trying to keep this 85 in his interest as he rode with some Rm 85's this weekend and keeps talking about them. I will admit the Rm's did sound alot throatier and I asked one of the dads and he said it was all stock....


I am running a #45 slow jet with the needle clip in the 3rd position.

The CR's do have a very different sound (higher pitched and more "tiney"). As you likely know, none of the mfg's have meaningfully changed the 85's in several years. I did a search on this forum as well as asked for input to make sure the CR is a competative bike before we bought ours. All indications came back that it has a strong motor but the lack of a power valve impacts low end torque. As the previous poster mentioned, keeping these in the upper end of the power band will help.

If you have not changed the rear sprocket then I would also do that. As mentioned, we added a tooth and that helped as well. My son is larger than most 85 riders at 5'8" & 130 lbs yet he is competative on holeshots and acceleration out of corners (still needs to go faster through the corners).

  • frdbtr

Posted August 04, 2010 - 05:39 AM

#6

hi. My son has a 04 cr85. I was wondering if it is worth it to change the reeds to aftermarket? And pipe, already have the r 302 shorty on it.I was looking into the boyesen reeds. I was also considering getting a whole new assembly like the v force 3 or Rad valve. It just seems underpowerd until it hits the powerband in the higher r's. I live in Michigan also. Anyone out there in a similar climate with some jetting specs would be good.
Thanks......


Have Eric Gorr put a 52mm piston in it and port it for low end lol! Seriously though, the shorty silencer and vforce reeds is supposed to increase the 85's low end. And like was already said, 1 tooth larger on the rear sprocket.

  • JJRace

Posted August 04, 2010 - 12:31 PM

#7

There are a few cheap ways to help the bottom end.

First is to get a thinner base gasket. Cometic makes one. That will slightly up the compression. put some new rings in at the same time.

Second, get a Pipe spacer from MXBonz

And add 1T to the rear sprocket like suggested

  • SubTexel

Posted August 04, 2010 - 12:59 PM

#8

For my nephews 07 CR85 I ended up throwing a full FMF system (Factory fatty and shorty), geared it up two in the rear, RadValve (yeah, I'm sold on the radvalves after wasting money on the VF3 for my CR, and dropping the VF3 for a radvalve on my 2010 KTM...), and threw a Wiseco forged HC piston in, run 60/40 avgas mixed with pump gas and it rips hard (also rejetted it, I'd have to tear the carb apart to look @ what finally worked best. I did have to lean it out quite a bit though).

Those mods seemed to be the best bang for the buck, and really opened up the usable RPM range. Though, it still isn't as good as an RM85 with the same mods in the hands of a novice.

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  • m320

Posted August 04, 2010 - 07:27 PM

#9

The rad valve will give it more bottom end ...You will feel the difference...

  • malburg114

Posted August 07, 2010 - 11:38 AM

#10

i also have an 07 cr85rb expert. We have a pro circuit complete pipe and unless you geet the jetting just right it doesnt help. we have changed the piston and reeds and nothing seems to help the bottom end. you just have to keep it in the power band and be in the right gear. and also we put the biggest sprocket on the front and that didnt help so we took away 2 or 3 teeth in the back and that helped a lot for the top and a little for the lower gears bottom end

Harrison

  • JJRace

Posted August 07, 2010 - 12:09 PM

#11

i also have an 07 cr85rb expert. We have a pro circuit complete pipe and unless you geet the jetting just right it doesnt help. we have changed the piston and reeds and nothing seems to help the bottom end. you just have to keep it in the power band and be in the right gear. and also we put the biggest sprocket on the front and that didnt help so we took away 2 or 3 teeth in the back and that helped a lot for the top and a little for the lower gears bottom end

Harrison


Your gearing is why you have no bottom end. Went the wrong way on both ends for more acceleration

  • ajabuell

Posted August 09, 2010 - 12:52 PM

#12

You guys seem to know 2 strokes, so I will ask this. I am short 5 foot 135 lbs I have a 150 r with a blown motor and just hate the fact of work required to keep them working. I bought it used and it blew up the top end 45 min of riding. (will keep as project bike) Found and 06 cr 85 big wheel for 2000$ looks great. But all I do is hare scrambles and play in the woods some mx but not much. Can I make this CR 85 work for me with info from thread or buy a new 150 R as the wife is willing to do.?? Sorry to cut into your thread.

  • frdbtr

Posted August 09, 2010 - 01:00 PM

#13

You guys seem to know 2 strokes, so I will ask this. I am short 5 foot 135 lbs I have a 150 r with a blown motor and just hate the fact of work required to keep them working. I bought it used and it blew up the top end 45 min of riding. (will keep as project bike) Found and 06 cr 85 big wheel for 2000$ looks great. But all I do is hare scrambles and play in the woods some mx but not much. Can I make this CR 85 work for me with info from thread or buy a new 150 R as the wife is willing to do.?? Sorry to cut into your thread.


$2k seems a bit on the high side on the price but if I were your size, I would be all over a CR85rb. You can do so much with them. I would take that bike, send the entire engine to Eric Gorr, have him stroke the crank and bore it to 52mm on the piston (ends up being a 112cc bike) get the porting that works best for you, set up the suspension and have a blast. My son has a stock crank with the 52mm big bore kit(103cc's) with low to mid porting from Eric Gorr and that thing had no problem taking me up some pretty steep switch back trails on a mountain ride that was over 8000 feet above sea level. (I am 6' 165lbs) It wasn't jetted even close to where it should have been for that altitude and had stock gearing. If I had geared it down and had it jetted properly, it would have been even better. (I had to use the clutch a bit to keep it higher in the RPM's).

EDIT: thought I would clear something up from above. I have an 05 450r so I wasn't just riding the mini bike but my son didn't have the courage to do some of the steeper trails on this ride.

  • malburg114

Posted August 09, 2010 - 01:48 PM

#14

You guys seem to know 2 strokes, so I will ask this. I am short 5 foot 135 lbs I have a 150 r with a blown motor and just hate the fact of work required to keep them working. I bought it used and it blew up the top end 45 min of riding. (will keep as project bike) Found and 06 cr 85 big wheel for 2000$ looks great. But all I do is hare scrambles and play in the woods some mx but not much. Can I make this CR 85 work for me with info from thread or buy a new 150 R as the wife is willing to do.?? Sorry to cut into your thread.


man all i use my cr 85 big wheel for is hare scrambles!!! i love its got the top end and at times it has the bottom

Harrison

  • ajabuell

Posted August 09, 2010 - 03:40 PM

#15

thanx for all the info. now i have to make up my mind.

  • gruberyz

Posted August 10, 2010 - 11:46 AM

#16

you want a little bottom end get a KX100 or KTM 105 much easier to ride than the no powervalve CR85RB

  • mbelcourt

Posted August 13, 2010 - 01:57 PM

#17

MY SON HAS A 05 BW AND IT IS BORED OUT TO 52.5mm. WE WANT TO STROKE IT,WHAT IS THE BEST WAY TO GO ABOUT IT AND NOT USE THE WHOLE SAVINGS.





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