Great CR 80 mods. Low end??YES!!!

Rcannon

Subscriber
Joined
Nov 17, 2001
Messages
1,886
Likes
0
#1
Yes. I think I did it! A CR 80 trailbike.

Obviously there are a thousand bikes better suited for the purpose. BUT..we owned a CR 80.

Step one. Replace blown cylinder with a 2004 model CR 85. Needed the 47.5mm piston as well. This cylinder bolts right on with no other mods. Head is the same.

Dont worry about the different upper end, small rod bearing. The new spec is different, but either the old or new one work wekk. I like the older bearing. It is slightly wider.

This gives a hint of low end to the bike without doing anything else. Not much, but a glimpse.

The real key is this http://www.mxbonz.com/plates80250.jpg

You can buy one from bonz, but I made my own. Use something at least 5mm thick. This makes the low end rideable.

The finishing tuch is three or four intake gaskets. I could not find a source for a CR 80 intake spacer. The gaskets worked very well.

These mods will let a 250 lb guy start off the line without slipping the clutch! Total cost is under 20.00.

Do this to your CR 80. Do it now. It is that worthwhile.

Oddly enough, top end power is still very good. The midrange rips.

Now, the next step is sending this beast off to a certain MR Gorr for low/mid porting.
 

bedell99

Subscriber
Joined
May 3, 2000
Messages
788
Likes
0
#2
Thank you very much for the info. I have been having so much trouble thinking of ways to get more low end. I tried a 14/56 tooth gearing and it didn't really do anything but give it a hard hit. How much did you pay for the cylinder. I was also thinking of trying a phathead with a high compression dome.
I'm definetly going to try a spacer with the gaskets on the intake and see how she like it.. Also what jetting are your running, I see you are up at altitude. Right now I have a 118 main, 2nd clip stock needle, 48 pilot.

Erik
 
Joined
Dec 20, 2000
Messages
160
Likes
0
#3
I ordered the spacer ring yesterday, and will post after I have a chance to install it. I also ordered the Moose Torque Spacer, so that that to try also. I would go with a Low/Mid port job, but do not want the bike down for 3 weeks right now.

We ride at sea level, in California.

Mike
 
Joined
Dec 20, 2000
Messages
160
Likes
0
#5
Well, the Bonz spacer, www.mxbonz.com. goes in the exhaust port, the Moose torque spacer goes on the carburator side at the Reed Block. While the Bonz spacer simply claims more low end, the moose spacer says it shifts the power band by several hundred RPM.

If you do a search on each of these there is plenty of posts, some say it is a waste, others say it is great. That may have to do with the bike, or other factors, but I am going to give it a try,

Mike
 

bedell99

Subscriber
Joined
May 3, 2000
Messages
788
Likes
0
#6
Hey Mike,

I understand it goes on the carb side, but does it go between the reed valve and cylinder or reed valve and carb. I would think it goes inbetween the cylinder and reedvalve.

Erik
 

Rcannon

Subscriber
Joined
Nov 17, 2001
Messages
1,886
Likes
0
#7
[Mike, if you get a chance, let me knwo how you liek the intake spacer. I believe it is going to be worth the money, for sure.
 
Joined
Dec 20, 2000
Messages
160
Likes
0
#8
I spoke with my local honda dealer, and he had good things to say about the reed block spacer also, so we will see. I am not sure which side of the block it goes on, but it is due to arrive next monday, I will post info soon as I can see the instructions and get it installed,

Mike
 

BAT

Subscriber
Joined
Oct 21, 2002
Messages
19
Likes
0
#10
Moose spacer available for the KX????

One of the Boys is riding a KX 85. Do you know if they make the intake spacer for the KX85?

Thanks

Also: where did you order the Mosse intake spacer - I need for Honda and Kawasaki (if they make it).

Thanks again.
 

bedell99

Subscriber
Joined
May 3, 2000
Messages
788
Likes
0
#13
I went and bought the moose reed spacer. I will give report on she likes it on next week. I'm really hoping this works. I'm starting to think this was the totally wrong bike for her.

Erik
 
Joined
Dec 20, 2000
Messages
160
Likes
0
#14
Well I just completed my mods on my sons CR80.

The Bonz exhaust spacer made a noticable difference. Proper jetting made a difference also. I found I moved the stock jetting worked fine, but with the needle all the way to the top.

The moose spacer helped also, but the next big bang for the buck was a 1 tooth lower front sprocket.

All in all, I put on the Bonz spacer, the moose spacer, new Power reeds from Boyesen, and a new chain and sprockets. Tested on the street infront of the house, will ride the trails this weekend,

Mike
 

Rcannon

Subscriber
Joined
Nov 17, 2001
Messages
1,886
Likes
0
#15
Mike, if you have a chance to post back, please mention how the top end power is changed by the mods. I did not notice a difference on our bike.