Author Topic: Drag Bike / The Big 4 Express. (Read 66008 times)

Don R · « **Reply #550 on:** November 25, 2022, 04:33:19 PM »

The 550 fork tubes got here today and got assembled in the #341 lowers, with a 1" lowering spacer and no load they sit a little higher than the 2" lowered 750F forks but have a lot more travel before they bottom out on the lower triple trees. I trimmed the 750 springs 1 3/4".
The real 550 forks had progressive springs in them, I need to give them a good cleaning and may use them in another bike. I noticed the franks forks had snap rings and removable parts in the bottoms while the repro tubes appeared to be pressed together.

Don R · « **Reply #551 on:** November 27, 2022, 11:29:25 AM »

I'm leaning towards using a stock F2 motor with the turbo, it's a low mile motor, the PO removed it at 8,000 or so miles due to not being able to get it running right. He had a known good runner sitting there. I'm thinking split the cases for inspection, new rings, hone and a port clean-up. Maybe a thicker base or head gasket to lose a little compression.

Don R · « **Reply #552 on:** November 28, 2022, 02:16:11 PM »

Here is a drag bike re-cap, for those who have lost track.
The first engine in this Dragbike thread is a stroker 72 x 69 mm which equals 1124cc. It has a new in box V&H header or it's original big tube 4-1 black pipe and a set of Weber carbs sparked by an early type ARD FM magneto. Engle cam and ported head.
The second Drag bike is raked and has a stretched swingarm, the motor is/was a turbocharged 836 with a Zenith/Bendix carb It has a mark II CD-ARD magneto. The rings are welded into the grooves, so it needs a set of turbo pistons and different cylinder. Time in the barn killed the sleeves and rings. Motor was built by a pair of former pro-stock motorcycle guys that remain un-named

Don R · « **Reply #553 on:** November 30, 2022, 02:59:51 AM »

The experts say 10.25/1 on 10 lbs of boost is safe if burning E85.

grcamna2 · « **Reply #554 on:** November 30, 2022, 07:22:41 AM »

Quote from: Don R on November 30, 2022, 02:59:51 AM

The experts say 10.25/1 on 10 lbs of boost is safe if burning E85.

The 'quality' of Ca. 91 octane 'premium' is poor;even Chevron.. I do think 10.25:1 is doable as a max CR out here..

Don R · « **Reply #555 on:** December 01, 2022, 07:26:53 PM »

I'm thinking of running 85% Ethanol with 15% no lead race gas. If I run high octane gasoline it should have a Dyna 2000 with timing control. A boost operated timing retard would be beneficial. I have an MSD timing retard box, an MSD digital box with a crank trigger firing through the ARD distributor cap should be a no brainer. Just $$$ and wattage.
This is an exercise in why? Why not? For no good reason other than impress the gearheads.

Don R · « **Reply #556 on:** December 04, 2022, 02:51:27 PM »

Today I decided WTF and heated the old 836 turbo pistons with my maap gas turbo torch. When they got to a heat gun measured 400* I began to work on removing the stuck rings. I used an o ring pick to wedge the gap open and a modified flat blade screwdriver to tap the ends of each ring as they broke off and popped out.

I got all four flat top Venolias (I think) cleaned up, now I need to check the gaps to see if they just stuck due to rust and carbon of it the motor went lean and heat closed the gaps up to where new rings won't work.

Don R · « **Reply #557 on:** December 22, 2022, 03:53:59 PM »

I did cam oiling and checking today, what I figured out.
My "not much" compression ebay 836 in the diecast has a Kenny Harmon F cam in it. I now know it's bigger than the Engle J cam in my 1124 stroker. I think that motor should get a stock F2 cam again and the Kenny Harmon cam will go where there is sufficient compression to make it work.
I'm still thinking the turbo motor goes back to 836 flat tops with the F2 cam.
I'll leave the Engle cam where it came in the 1124 stroker and fix the cylinder sleeves to hold compression.

Don R · « **Reply #558 on:** December 24, 2022, 10:52:41 PM »

http://forums.sohc4.net/index.php/topic,32541.0.html

I want to park this here for future reference. Lord Moonpie got on a roll.

Don R · « **Reply #559 on:** January 31, 2023, 03:02:11 PM »

Tech tip, if you ever re-weld a spider header be sure it's bolted to a head first. I fought this thing for hours before I realized the welds didn't appear original and it was warped out of shape.
I welded up a set of tube spreaders and got the tubes to pop into the sockets on this old head, then I heated the tubes with maap gas hoping they will relax into this shape. Later I want to cerakote them.

Don R · « **Reply #560 on:** January 31, 2023, 05:00:51 PM »

I didn't get enough heat to make the tubes relax in the correct position but they are way better when I loosen the spreaders than they were. I did some polishing on the tubes, the metal is magnetic, I think what I see is a little nickel plating that's still there.
My plan is to get it running and assembled, test ride it and then take it back apart for refinishing.

Any ideas on bending the exhaust flanges back to flat again?

Don R · « **Reply #561 on:** February 03, 2023, 07:51:49 PM »

I got a fix for the stroker motor answered for me and I finally got the turbo header on the mock up engine. As soon as I feel a little better I'll hit it in the shop again. My first vacation in 3 years and I get sick, Wife tested + for covid, my test was - but I'm sure I have it too.

Don R · « **Reply #562 on:** February 05, 2023, 04:35:41 PM »

I hung the turbo intake and turbo on the exhaust, tried a couple of the head pipes I have and realized one has lugs welded on for a heat shield on both the header and head pipe, so they are a match.
I'm researching where to put the o2 sensor.

Don R · « **Reply #563 on:** February 06, 2023, 09:22:51 AM »

The alignment of the turbo intake and exhaust leaves a little to be desired, it has the big intake rubber in a bind. I believe Pegasus sells a turbo rubber that has a flex joint in the middle, in case I can't overcome the misalignment. It appears to be too long but who knows?

The turbo to manifold rubber that was on this setup had a notch that appeared to have been removed by a rodent. I bought a new turbo rubber and cut it to the same length. Today I realized it's too long and the notch was put in there not by a rodent but by a PO that didn't take it off and re-cut it to length. My mistake, I wrapped it with masking tape to make a straight line and re-cut it with a razor knife.
The turbo lines up much better now. It's still too heavy to just hang off the carb rubbers, I don't see an obvious hanger mount location and the float bowl seems like it should be more level. Film at 11.

Don R · « **Reply #564 on:** February 13, 2023, 12:54:26 AM »

Engine #1 stroker
I took the 1124 back apart this weekend, having covid is keeping my time open. Anyway, I re-split the cases, this time from the top, I was surprised how much fuzzy stuff was left in it from the rotating assembly eating the cylinder o rings. I'm sending the cylinder and pistons off for sleeve re-setting, a quick hone job and new rings. There was a problem with the shift drum, something wasn't together quite right and the thin metal plate on the ratchet pins was bent over.
It does have stock length rods, new tensioners and there are grooves on top of the oil pump where the primary tensioner or chain had failed once. The mains still look good and the rods are still snug on the crank pins, I've considered swapping to the new set of MTC aluminum rods, I'm less fond of the machining around the rod bolts on the new ones than the ones in the motor already. The cam chain has a tight spot inflicted by me. I allowed the chain to bunch up when I rolled the motor over.

Don R · « **Reply #565 on:** February 13, 2023, 04:54:21 PM »

The main bearing areas in the crankcase were all marked with yellow paint. I replaced the mains with yellow bearings and checked with plasti-gauge. After it never running due to multiple issues I took it back apart. The bearings have shiny rub marks on one side and look new on the other side. What's odd is they alternate, shiny on top, next one bottom, next one top, then bottom, then top. I did use lucas assembly lube on them and got oil pressure with a pressurized cylinder before spinning the motor.
My plan is to replace the shiny ones with black mains and re-check.

Today I noticed a ruined piston, I'm seriously considering just building a new motor. With the welded stroker and aluminum rods I always knew it's on borrowed time. With the wonky main bearings, seriously scuffed piston, scraped oil pump, It may be time to freshen up the head and install a new motor under it.

Don R · « **Reply #566 on:** February 15, 2023, 09:58:45 PM »

I re-read most of this thread. What it boils down to is that it took me 10 years to abandon the drag bike a piece at a time. It seems like a K0 or K1 always comes along and jumps the line.

I have a better titled and licensed frame now with the 836 Hot Rod bike, I'm going to press on getting it running so I'll have something to beat on this spring.
The Big 4 express is now going to be the raked and extended frame, The former turbo engine will be the base for its motor, possibly an F2.

Terry in Australia · « **Reply #567 on:** February 15, 2023, 11:35:05 PM »

It's not that much different with me Don, I'm easily distracted so was surprised that I've almost finished getting the Fireblade and RC51 ready to sell, considering that the blue F2 rolled into my life recently, and now that I might have a Kawasaki Mach III on the boil as well, I need to slap some sense into myself and move some bikes before the weather turns to mud. You can only do what you can do.

Don R · « **Reply #568 on:** February 18, 2023, 09:58:45 PM »

I went ahead and fitted the crankshaft studs and while I was looking at the bottom of the motor found evidence of weld repairs. This beast kicked out a #4 rod once upon a time, it holed the bottom of the case and removed the points mount inside the case.
What I'm thinking now is a stock stroke big cc motor and the turbo on it with just a little compression so it's not a dog at low rpm's and a safe tune-up on E85.
A friend is a Harley Davidson tech. He has his own shop and is familiar with HD fuel injection. I intend to pick his brain about what efi might work where this HD carb currently resides on the turbo.

Don R · « **Reply #569 on:** February 24, 2023, 10:28:28 AM »

I found a deal on black cb750 code main bearings on ebay so I bought all 10 they had for under $87.92, I also got a pair of base gaskets for $11.20 shipped. I read RC always used black ones. My buddy in the 750 business always used green.
it was suncoastcyclesports.
They must be eliminating old stock.

PeWe · « **Reply #570 on:** February 25, 2023, 07:54:36 AM »

Good idea to measure the clearance.
You have started a good thread about this before.

http://forums.sohc4.net/index.php?topic=165595.0

" For any sort of life and particularly for racing .0018" is the figure. "
My cranks and latest rod measurement have been closer to .0020.
Encouraged to provide good oil flow.

Interesting point that sealer will add a little bit more

Don R · « **Reply #571 on:** February 25, 2023, 10:26:55 AM »

I'm seeing these bearings getting more expensive, hopefully these will be of some use in the future. They didn't have an assortment listed or I would have purchased more colors. My guess is they ordered them for someone who didn't pick them up. Under $9.00 each seemed like a deal.

The twin cam manual has a bearing shell thickness chart that shows the bearing thickness and corresponding color. My dial caliper does not have the ability to measure the difference between bearings.
The alcohol dragster owner that I crewed for measures the shell thickness at the bottom to determine when to replace their rod and main bearings. It was interesting to watch them tuning by the bearing condition.

Don R · « **Reply #572 on:** February 25, 2023, 10:58:26 AM »

http://forums.sohc4.net/index.php/topic,165595.msg1913140.html#msg1913140
I appreciate all of the help from the members back then and now. Reading my older posts I feel like I'm one of those guys that doesn't listen to good advice. It's been 6 years and several other bikes have come and went while this chunk sits waiting. It's easy to forget what I did and when.
I'm going to swap to a less abused crankcase and have a pro choose the bearings. That guy will also decide if this crank is a wise choice, I'm guessing no, and I'm better off to build a 970 using a 10,000 mile 10 oil change case and crank I have.

I can add to this, after trying to start it, each main bearing shows wear, which alternates top to bottom in each main. This motor has had extensive clearancing for the aluminum rods and stroker crank and shows signs of previous weld repair. I won't be using it in a build at this point.

PeWe · « **Reply #573 on:** February 26, 2023, 12:28:46 AM »

I found your thread when I was looking for recommended rod bearing clearance (modified engine) a few weeks ago and my old crank bearing job where looser than stock was recommended.
http://forums.sohc4.net/index.php/topic,155014.msg1774464.html#msg1774464

This is the good thing when writing about it here, possible to find it for next time, all good comments that helps too.

RAFster122s · « **Reply #574 on:** February 26, 2023, 03:56:19 AM »

Would need micrometers to make precision measurements...

Or plastigauge when measuring between rotating parts like rods and rod bearings and cranks and crank bearings...

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Author Topic: Drag Bike / The Big 4 Express. (Read 66008 times)