Topic: Project B7 Underway! Billet Big Block Built By Bill BentON Racing

[kmb69]

I have received a few PM's with questions this post may resolve.

I'm not going to bad mouth anybody else's product, but Kenny's kit is absolutely superior to any I have seen. His dampers appear to be the exact spec for stock and/or high performance applications. At least as important are the 1/4" FHSCS bolts. The M6 FHSCS are nominally .015" smaller OD which is quite a bit at this diameter. The hole in the hub is nominally .209/.210" which is the perfect minor diameter for the 1/4"-28 screws and nominally .013" too big for the M6. When you consider you are replacing Honda's rivets with screws, it's a no brainer. You can rather easily strip the threads using the M6. You can bend a Bondhus 5/32" hex wrench installing the 1/4"-28 screws without pulling the threads. They are SOLID. I also used Red Loctite on the threads. The side plates need to be machined precisely for the larger screws and the Imperial screw has a 82 degree countersink versus the 90 degree on the Metric screw. I machined the side plates so the screws would barely go through and the thicker Imperial head stands proud approximately .050" which easily clears the bearings.

My advice, especially to the racers, is use the Cycle-X kit or have Kenny rebuild them to achieve the highest level of confidence.

[slikwilli420]

Keith, I just redid a primary hub for my racer and found that the rivet holes were within 0.001" of the American equivalent tap drill size for M6x1.00, which is 13/64" or 0.203" so I tapped mine to M6 and used grade 10.9 screws as supplied with my kit. I applied red Loctite and was able to achieve the recommended 84in-lbs of torque on all 12 without issue. I hear you about using the 1/4" screws but with red Loctite and a staked screw head, there is still no way they will come apart.

[kmb69]

Keith, I just redid a primary hub for my racer and found that the rivet holes were within 0.001" of the American equivalent tap drill size for M6x1.00, which is 13/64" or 0.203" so I tapped mine to M6 and used grade 10.9 screws as supplied with my kit. I applied red Loctite and was able to achieve the recommended 84in-lbs of torque on all 12 without issue. I hear you about using the 1/4" screws but with red Loctite and a staked screw head, there is still no way they will come apart.

The nominal proper minor for the M6-1.0 Class 6H is 5mm or .1968". The nominal proper minor for the 1/4"-20 Class 2B is .201". The nominal proper minor for the 1/4"-28 Class 2B is .213". The hole in all the hubs I've checked is .206/.210". You can only achieve full thread engagement, per nominal thread specs, with a 1/4"-28 screw.

I'm not saying the M6 won't work, I have used both but the 1/4"-28 screw is noticeably more robust.

[PeWe]

Another good improvement to consider I think I need to check which rubbers that is used in my rebuilt primary drive.

[bear]

Found a pic of an  old drive taken from one of our motors, thought it might be of intrest.
It's fairly typical of the units we removed during our 100hr rebuilds.
Notice the condition of the limit pins.

Cheers,
Brian

[slikwilli420]

Brian, aside from the pins, is the rest serviceable?

[bear]

Almost allways the rubbers would be fractured through the center.
If they failed completely (and it did happen) the shock loads would result in failure of a drive line component.
Usually a gearbox.

We would probably reuse the drive pictured after replacing the rubbers & upgrading the pins.


Cheers,
Brian

[kmb69]

Found a pic of an  old drive taken from one of our motors, thought it might be of intrest.
It's fairly typical of the units we removed during our 100hr rebuilds.
Notice the condition of the limit pins.

Cheers,
Brian

Wow! You guys were banging those suckers! 

[slikwilli420]

Almost allways the rubbers would be fractured through the center.
If they failed completely (and it did happen) the shock loads would result in failure of a drive line component.
Usually a gearbox.

We would probably reuse the drive pictured after replacing the rubbers & upgrading the pins.


Cheers,
Brian

Makes sense. No apparent issues with the M6 hardware? I did mine with high grade M6 bolts, but Keith has me a bit nervous. Im racing but wont be shocking the gear the way a sidecar rig will be.

[bear]

Apparently I'm hard on gear Keith. 

[bear]

Makes sense. No apparent issues with the M6 hardware? I did mine with high grade M6 bolts, but Keith has me a bit nervous. Im racing but wont be shocking the gear the way a sidecar rig will be.

We have had them work loose once and grind into the side of the case unfortunately.

[kmb69]

.....
Makes sense. No apparent issues with the M6 hardware? I did mine with high grade M6 bolts, but Keith has me a bit nervous. Im racing but wont be shocking the gear the way a sidecar rig will be.

Tap one to M6 and tap one to 1/4"-28 and compare the amount/depth of threads. There is a significant visual difference and very noticeable difference when torqueing the screws.
How good will the M6 standup? Probably depends a lot on the precision of the countersink locations and particularly how much power you are making.
Brother Bear is making 135-150 (or more) RWHP! 

[slikwilli420]

.....
Makes sense. No apparent issues with the M6 hardware? I did mine with high grade M6 bolts, but Keith has me a bit nervous. Im racing but wont be shocking the gear the way a sidecar rig will be.

Tap one to M6 and tap one to 1/4"-28 and compare the amount/depth of threads. There is a significant visual difference and very noticeable difference when torqueing the screws.
How good will the M6 standup? Probably depends a lot on the precision of the countersink locations and particularly how much power you are making.
Brother Bear is making 135-150 (or more) RWHP! 

I'll be more in the 80-85hp range, but I did find that the M6 tap gave good thread engagement and that the holes in my hub were smaller than you had observed. I was also able to achieve proper torque on each bolt. They will be staked as well.

[kmb69]

.....
I'll be more in the 80-85hp range, but I did find that the M6 tap gave good thread engagement and that the holes in my hub were smaller than you had observed. I was also able to achieve proper torque on each bolt. They will be staked as well.

Quite possible Honda changed the rivet/hole size in certain revisions.
Not sure since they saw it as an unserviceable item, it's undocumented other than replacing the whole assembly.
I guess first step in making screw choice is checking the hole size in the hub.

[madmtnmotors]

I guess first step in making screw choice is checking the hole size in the hub.

Good advice. 

[dragracer]

I'll be curious to see how the kit from "across the water" holds up in my F model project, with the freshly rebuilt primary, when I throw a load of nitrous to it this season. My kill time between shifts will be shortened as much as possible to reduce the nitrous backfire. Something in the driveline will get a helluva shock as I move down track.

[bear]

I'll be curious to see how the kit from "across the water" holds up in my F model project, with the freshly rebuilt primary, when I throw a load of nitrous to it this season. My kill time between shifts will be shortened as much as possible to reduce the nitrous backfire. Something in the driveline will get a helluva shock as I move down track.

Do you launch in 1st or 2nd gear Frank?
If it's 1st say a little prayer as you grab 2nd.

Cheers,
Brian

[dragracer]

I'll be curious to see how the kit from "across the water" holds up in my F model project, with the freshly rebuilt primary, when I throw a load of nitrous to it this season. My kill time between shifts will be shortened as much as possible to reduce the nitrous backfire. Something in the driveline will get a helluva shock as I move down track.

Do you launch in 1st or 2nd gear Frank?
If it's 1st say a little prayer as you grab 2nd.

Cheers,
Brian

Hahaha. I leave the line in first gear and on a no bar bike, I normally won't start spraying nitrous until I'm 2 seconds into the run. I like to get well past the 60' mark before the nitrous kicks in on a progressive controller. I'm sure it'll be in 2nd at that point.  I typically start at 20% and then ramp it up as I go down track.  The final percentage is usually set dependent on how quick I want to go and what size jets i'm running at the time.

[Bill/BentON Racing]

Now that's a primary, thank you Kenny and Keith.  One pictured is a CycleX plug and play all new bearings and balanced also! Bear ,hopefully these new gears will hold up for 2nd....

[POPS 911]

Bill: With all those new parts I can see a new record for the SOHC 750 based motors ?
At MAN CUP 42 I will have the TURTLE [400CC] ST/ET and my CM450A  like brand new for the SEL class both SOHC 2 cyl.

 POPS BK911 and 911 too...... Get that turbo running I got cash.

[dragracer]

Primary looks good Bill. And I like the fact that its been balanced. Anything that rotates with the crank should be. Hopefully now you've got everything you need to start working on the engine. Time can sometimes slip by quickly.

Although I should have been working on an Sohc, I spent today getting one of my Kaw engines back together. Its been sitting on the work bench for 5 month's 😆. I need to get this one done and out of the way so I can get back on the Honda project. I've got a shop full of parts and pieces to assemble.

[scottly]

Billy, what's that gnarly looking chunk of metal lodged between the sprockets??

[Bill/BentON Racing]

Just one of the larger pieces of what once was number 3 RC lightwt 12.5 to 1 record setting lol piston! It shattered into this! I was lucky....

[scottly]

You may want to pry that chunk out from the sprockets before running it.

[Bill/BentON Racing]

Nah, it'll help balance it and extra tension on chains , Bill