Other DR650 Engine Mods

divemaster5734

divemaster5734

Anyone ever do performance mods to a DR650?
I'm trying to decide either the 780cc with new sleeve, or 690 with just a bore and high compression piston.
Will probably have the cam reground and have the big valves installed at the same time.
Already have a 1300 muffler, just waiting on the header and mid pipe before install.
Just wondering if anyone else has done this and what the result was.
Thanks
 
divemaster5734

divemaster5734

SRAD97750:
Only ridden the stock version. Sounds awesome either way!!! :thumb: -BIG DAN
Click to expand...
Trying to figure out the best carb right now.
It's either the TM40 FS pumper or the FCR-MX 39.
I know the stock 650 is a BST40. I hate the vacuum delay. I don't know if a jet kit and extra slide hole will be enough for the end product.
I'm a little hesitant to go down in size, but have a couple Yamaha's and really like the Keihin performance. They seem to be pretty bullet proof, just a pain to pull off. Have torn apart and cleaned 2 of them without a rebuild kit and no issues. Both bikes start 1st kick.
Being a mechanic, what's your opinion of the two?
 
josmoloco

josmoloco

divemaster5734:
Trying to figure out the best carb right now.
It's either the TM40 FS pumper or the FCR-MX 39.
I know the stock 650 is a BST40. I hate the vacuum delay. I don't know if a jet kit and extra slide hole will be enough for the end product.
I'm a little hesitant to go down in size, but have a couple Yamaha's and really like the Keihin performance. They seem to be pretty bullet proof, just a pain to pull off. Have torn apart and cleaned 2 of them without a rebuild kit and no issues. Both bikes start 1st kick.
Being a mechanic, what's your opinion of the two?
Click to expand...
tm40 :drool:
 
SRAD97750

SRAD97750

Moderator
Staff member
I have no experience with the TM40. I imagine it's performance is comparable to the Keihin accelerator equipped models.

As far as the Keihin FCR models... I love them. I have 4 FCR40s mounted to the GSXR. The accelerator pump system is amazing in these carbs, and adjustable too. The throttle is extremely responsive, and the slide rides on ball bearings maximizing smoothness. Metric allen nuts in both the bowl and slide cover minimize hardware stripping. Not a fan of the bowl adjacent idle mix screw, but you can't have everything...

-BIG DAN:thumb:
 
cleonard

cleonard

As they say there is no replacement for displacement. I say go for the cc's. I think that there is a 790cc kit now.

Speed costs, how fast do you want to go? The 790cc will be two or three times more expensive than just a new piston.
 
SRAD97750

SRAD97750

Moderator
Staff member
4 40mm's on a 750cc. Stock was 38mm VM Mikuni's.
This is no regular GSXR 750... less than 5000 miles since FULL rebuild, 14.5:1 pistons(up from 13.8:1), fresh valve job, yoshimura race exhaust, and Dyna2000 ignition with a rev limit of 15K rpm.
These carbs are jetted properly. Where you will use a 165+ in a single, I have 120's for main jets...

-BIG DAN:thumb:
 
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