Big bore kit/Dynammo Humm

Have you talked to Dynammo Humm about this? If not I would.

 

DynamoHumm does market the piston kit, but no longer does the rebuilds.

TTS in the UK has the piston kit for 400 pounds sterling, which comes from the same source as the kit from DynamoHumm.

Check here:

http://www.tts-performance.com/cata...72&PHPSESSID=c6d03f26dc6a84a1ed439202234a0e30

 

What kind of Hp boost do you get? Does it make the bike less reliable over the long haul? I have been told modifying internals change the motor forever and will never run as good.

 

big bore kit /dynammo humm

hay i have a 86 vfr750f i had dynammo humm install a 850 cc big bore kit and go threw my motor years back and im happy what a differance, i didnt know that dynammo humm was not rebuilding engines any more ?

 

DynamoHumm still offers the 840cc and the 870cc kits for the 750 and the 800, respectively. Both piston kits are through TTS. DynamoHumm (now Picotte Racing) no longer has a shop where they can do this kind of work. They still have the expertise but no longer the space.

As far as "running as good" as it did before...it's up to the quality of work performed. Some folks can ruin an anvil with a rubber hammer of course, and I would never let them near a box end wrench much less a VFR. I have heard nothing but positives about installed overbores on VFRs.

 

VFR big bore kit

I'm a very satisfied owner of Dynamo Humm's original 840 test mule engine. In addition to the big bore kit, it's been race balanced, has 1 mm oversized valves, a ported head with higher compression, the anti-backlash gears have been removed from the valve train, the PAIR plumbing is gone and it's been re-jetted. The exhaust is a Two Brothers header and low mount muffler. It makes 115 HP at the rear wheel. The increased torque is noticable from off idle to redline and it WILL pull to redline in 6th with stock gearing. I went up one tooth on the countershaft for more relaxed cruising, but I'll probably go back to stock, because too much clutch slip is needed from a stop and I live in the suburbs. Mileage is ~40 in the relaxed touring mode but drops to mid 20 when riding aggressively - it's jetted pretty rich and requires premium fuel.
Reliability is no different than stock, but rear tire life is shorter (I wonder why?) The engine deserved a suspension upgrade to make the most of it, so there's an Ohlins in the rear with some shimming to raise it ~ 1/2 in. Plus it has a Race Tech w/Gold Valves front fork conversion. I don't plan to sell this bike anytime soon. It has real sportbike power and handling with touring bike ergos that suit my 68 yr. old bod just fine!

However, as others have mentioned, Dynamo Humm doesn't do the work anymore. I know of one expert mechanic who has done his own conversion, but it's not a runner yet (RC51 front end is being installed). Dynamo Humm quit converting when VTEC came along.

Regards, Routemeister
Visit Routemeister's Backroads
http://home.rochester.rr.com/backroads/

 

what would be the stock rwhp on my vfr? I have added a 2 bro's exaust that is it. How much of a gain in hp would I have at the rear wheel?

 

Stock RWHP is 85 - 95, depending on condition of the motor. The 2 Brothers canister changes the sound, but makes no noticeable difference in power - certainly less than the variance quoted above. For a noticeable change, you need to change both the air filter & muffler (more air) and re-jet the carburetor (more fuel). Frankly, it's not worth the hassle nor the $ involved. The motor is happy enough spinning at higher RPM, so if you want more acceleration, go up a couple of teeth on the rear sprocket or down one tooth on the countershaft sprocket (~ equivalent to +4 teeth on the rear sprocket, but chain life is shorter)
Regards Routemeister
http://home.rochester.rr.com/backroads/

 

Come to COTU in Marietta next spring. It will be there & just the noise it makes is music to my ears, what with rumbling exhaust and clattering gears in the valve train.
Routemeister

 

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