Author Topic: Frankenmotor? (Read 3831 times)

Jerry Rxman Griffin aka MuthaF'er · « **Reply #25 on:** August 16, 2020, 10:24:09 PM »

That is Wilbur. He rarely pulls the wheel and usually makes 2 - 4 rounds each meet. Pretty consistent.

johno · « **Reply #26 on:** August 16, 2020, 10:53:51 PM »

good pic Wilber , luv ya style man.

I couldn't tell if it was you or 754 but I should have remembered Franks pics are so old their almost black and white.

sorry Frank, you'll get your chance hehe

bear · « **Reply #27 on:** August 16, 2020, 10:59:23 PM »

I don't mean to tell my granny how to suck eggs Johno but......................
Re that cush drive, I've had those counter sunk machine bolts work loose, even though they where loaded with lock-tight. Center punching a small dimple on the outer edge of each bolt did the job though.
I know you would be all over it but I thought I would mention it for my own peace of mind.

Anyway carry on.

Cheers,
Brian

johno · « **Reply #28 on:** August 17, 2020, 01:04:16 AM »

Thanks Bear , good tip, I'll follow that up as not in yet.
Remember Im skinnier than you, so less load hehe.

madmtnmotors · « **Reply #29 on:** August 17, 2020, 04:06:47 AM »

Quote from: johno on August 16, 2020, 10:53:51 PM

good pic Wilber , luv ya style man.

I made it to the fifth round that day. The picture was round two when my opponent broke in the water box, free pass! I was going for broke trying to cut a quick light for a potential bye run in the next round.

Sam Green Racing · « **Reply #30 on:** August 17, 2020, 03:00:09 PM »

Wilbur, is you bike still a 750 ?

754 · « **Reply #31 on:** August 17, 2020, 10:17:01 PM »

I alway slip the clutch , often get wheel up but not to high, or I try to feather cluck back.. not an issue with longer swingarm.
Even on the dirt track with a street tire on my XL 350 , I would come out the hole.. wheel up.. sometimes as high as Wilbur..

madmtnmotors · « **Reply #32 on:** August 18, 2020, 04:18:13 AM »

Quote from: Sam Green Racing on August 17, 2020, 03:00:09 PM

Wilbur, is you bike still a 750 ?

Sam! Good to hear from you. I am now up to 836cc with C.I.'s flat top pistons but it's still a little anemic being near stock compression. Running 16/52 sprockets to help with 60' times and a 79' swingarm (+2") to help keep the front end down... most of the time.

I've got a GSXR swingarm in the wings courtesy of dragracer Frank and I hope to do a higher compression build, probably sometime next year. Of course that will require shoring up the bottom end. It's always something...

Sam Green Racing · « **Reply #33 on:** August 18, 2020, 12:24:48 PM »

Quote from: madmtnmotors on August 18, 2020, 04:18:13 AM

Quote from: Sam Green Racing on August 17, 2020, 03:00:09 PM
Wilbur, is you bike still a 750 ?

Sam! Good to hear from you. I am now up to 836cc with C.I.'s flat top pistons but it's still a little anemic being near stock compression. Running 16/52 sprockets to help with 60' times and a 79' swingarm (+2") to help keep the front end down... most of the time.

I've got a GSXR swingarm in the wings courtesy of dragracer Frank and I hope to do a higher compression build, probably sometime next year. Of course that will require shoring up the bottom end. It's always something...

Wilbur, are the 836 flat top pistons similar to the standard 736 ones ? If so, the compression will be probably be a little higher than stock because you are pushing an extra 25cc per piston into the same size combustion chambers. Just a thought mate.

Hope you are well and staying safe Wilbur.

Sam.

madmtnmotors · « **Reply #34 on:** August 18, 2020, 02:02:21 PM »

Quote from: Sam Green Racing on August 18, 2020, 12:24:48 PM

Wilbur, are the 836 flat top pistons similar to the standard 736 ones ?

The K8 pistons had a slight dome so I figure the bigger bore brings the flat top pistons back to near stock compression. I think the combustion chamber is different on the later heads. I purposly avoided a higher compression build so I would not have to rip the cases open. A high compression build is on the drawing board though!

Sam Green Racing · « **Reply #35 on:** August 18, 2020, 04:30:08 PM »

Cheers Wilbur.

bear · « **Reply #36 on:** August 18, 2020, 11:50:59 PM »

I'm pleased to see you on deck Uncle Sammy.
I hope your picking up a bite.

Cheers,
Brian

PeWe · « **Reply #37 on:** August 19, 2020, 12:17:42 AM »

392 heads have 24cc chambers according to CycleX.
Earlier 22.5cc.

I have a 392 head in a box, chambers look bigger, almost like my ported K6 head (24.4cc). Smoother hemi shape.

I installed K7,K8 (392) pistons in my K2. + 0.5mm. cheap from Cruzinimage.
Compression increased from 140-150PSI to 170-180PSI.
Runs fine with stock K6 head

Sam Green Racing · « **Reply #38 on:** August 19, 2020, 03:33:31 AM »

Quote from: bear on August 18, 2020, 11:50:59 PM

I'm pleased to see you on deck Uncle Sammy.
I hope your picking up a bite.

Cheers,
Brian

Thanks Brian but I do look in every day when possible but I don't often post, just a quick read to see what's going on.

Sam.

johno · « **Reply #39 on:** August 19, 2020, 03:53:43 PM »

Are You talking about this bloke Bear,

Sam Green Racing · « **Reply #40 on:** August 20, 2020, 08:14:50 AM »

hahaha, back from when I was good looking.

That was in Mike Rieck's workshop early 2010 Johno.

timtune · « **Reply #41 on:** August 30, 2020, 07:33:42 AM »

I,ve been reading thru the whole thread again and I'm beginning to think the tranny gear swap is a bit of a rats nest and I'm probably better off leaving the F tranny alone and just playing with sprockets. Much easier.

That said I'm now a bit confused about the output shaft being 10mm farther out (78 F motor). How can I square that with my earlier frame swing arm setup? AND just to confuse things I am running early Comstars with a triple disc set up. Not sure what year but they are the older style (metal edges of stamping faced in rather than out) would they have come witha larger chain? I installed these almost 20 years ago so I can't recall if I added a spacer or what.

754 · « **Reply #42 on:** August 30, 2020, 08:51:13 AM »

You have to modify things to run long shaft with early frame/ swingarm combo.
COMSTARS NEVER CAME on shorter shaft bikes.

timtune · « **Reply #43 on:** August 31, 2020, 07:57:33 AM »

"COMSTARS NEVER CAME..."

That's what I thought. I put those wheels on almost 2 decades ago and can't remember if I built some kind of spacer. I almost recollect I did but the ol memory has faded so much..

Maybe I crack open another K motor and sub in the short shaft. Is it just the output shaft and one mating gear that needs the swap.

754 · « **Reply #44 on:** August 31, 2020, 08:04:37 AM »

If you have short shaft motor, and use later wheels, BUT USE your ORIGINAL sprocket holder and inner spacer, it would all line up.

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Author Topic: Frankenmotor? (Read 3831 times)