Topic: Drag Bike / The Big 4 Express.

[Don R]

Flip blue and yellow wires

I would if it had any!  Edit, I flipped green and gray and it ran for a few seconds. It sounds awful, I'll check the cam chain tensioner and clutch before trying again.

[Don R]

I hit it again, it sounded better, I hand oiled the cam, rockers and chain. It seemed to be pumping some oil to the top also. The PO had concerns about the valve train. I already pulled the cam caps and they are as smooth as can be. Valve lash seems normal and no valves hanging open.
  Edit,
 I put on 400f bars, a better clutch perch, Magura levers, a good master cyl, a better quarter turn throttle, a better cable and a big throttle grip. It turns slightly easier. The header clamps are soaking in vinegar.
 Mailman came, turbo gaskets are here. Not sure which ones, I saw a set and bought it.

[Medyo Bastos]

That help you out?


Sent from my iPhone using Tapatalk

[Don R]

Yes it did, thanks. I had considered it but hadn't taken time to sort the birds nest of wires. I followed the coil wires, the rear black ones went to black but the front black ones went to two other colors in the Gerex harness. I swapped them, luckily they were in bullet connectors.
 I got the spreadbore carb rubbers, Andrews motorsports shipped them promptly. They show metal core gaskets on their site, I may order a few of each. They had an 850 kit with cylinders listed, too bad it's also sold. They do have other big bore kits in stock.
 Did you get the A converter back? I'm still sitting on a 750A long block in case someone needs parts.

[Don R]

 Outside today, it has brakes now. Stopped running since I hooked up brakes, throttle cable etc. The carb slides may be closed. 1987 license plate wow. I started trimming a set of lower frame bars for it to use the last set of bolt in connectors. If I do more frames, I'll use weld in's from cyclex. 

[Don R]

 My brother was looking for some wire today and checked an old toolbox. He found and brought me an old right control bottom, kawasaki point cover, a couple odds and ends, a flywheel puller for something not sohc and two "new in package" green cb750 rod bearings.

[Alan F.]

Old tool boxes are the best.

[Don R]

 Bike #1, Theory,
  I read they used short rods on the stroker cranks to allow the pistons to have standard pin height. If that is true, I could use a stock stroke crank and the set of MTC rods on the existing pistons in the stroker motor. That would still make it over 1,000cc and remove the threat of the welded stroker breaking. The guys in the know say it's a matter of when, not if, it will fail.

[Don R]

 My choices of swingarms for the turbo bike appear to be 18"stock, 19" stretched stock, 20" box tube and 24" clubfoot box tube. I'm thinking longer one will look odd but keep the front end down the best. I have 750 or 550 fork tubes to get low as he11 in the front since the exhaust doesn't go under the bike, ground clearance might not be an issue, and fender clearance might not be a problem with the 37* rake.
 I have a good place for the 19" swingarm, on the hot rod bike.

[Don R]

 The RC bike got a set of UPP carb rubbers for the 29 smoothbores recently from Andrews motorsports. Apparently, they don't make them anymore and are made of urethane instead of rubber. I thought they were awfully shiny.

[PeWe]

Are those rubbers harder than the rubbers sold first half of the 80's that were way too soft?

Mine pulsated even from idle and not strange they cracked within 5000 km.
Power must have been lost when rubber collapsed instead of sucking air/fuel.

(My car had boost surges thanks to stock bad collapsing turbo inlet pipe in plastic. Alu tube pipe from US tuners improved that.)

I adapted my VM29 setup to use stock rubbers.  Rack cut, 12.5mm removed, welded together again so carb 1-2 sit closer to 3-4.

Had to grind off some on the fuel T connection. It did not leak fuel with  shorter parts into carb 2 and 3.
A domino effect to drill new holes in throttle rod. For throttle mechanism, throttle 3, 4  and cut it after 4. Holes were not absolutely not in line, possible to adjust when bench synching them.
Choke mechanism.had to be vandalized some for 3,4.

I used them 2014, new carbs 2015.
All carb jettings after the never ending rebuilds has given me good experience I can use on my VM29"s if using them again. I remember I fiddled with pilot jet, air jet, needle jet, needle height and the easiest of all, main jet.

A new bad ignition wire with intermittent issues made jetting and test rides to a nightmare. Found out after I replaced the carbs and wire got even worse with the new set of carbs.
Copper leads after that.
Stiff copper leads after some soft flexible copper wires glided out from the Dyna coils causing issues.

It seems that most VM29 users set air screw to 1/2 turn.

I do not like way too rich for a longer period.  Internal cleaning might be needed.
Take head off to clean pistons, chambers and ex valves + ports from carbon and thick layer of soot can be needed.

Frame kit is really mandatory!

[Don R]

 These "rubbers" seem fairly solid, Sudco shows upp brand on their web site but upp shows nothing.

 This bike has a cutaway frame and I'm in the process of restoring it with a bolt on kit. (The triangle will require a weld) I'm also hoping the PO has it well jetted. He had removed a lot of the goodies before banishing the frames to the farm.
   I'm trying to put it back to its last running condition before doing much restoration. I'd like to hear the RC engine run first and check the transmission. It has the re-jetted stock carbs on it now, I put them on before getting the manifold adapters.
 I did see a re-rack kit for the 34 mikuni carbs that had drilled shafts etc. That would help a lot with them.
 1/2 turn is good info, thanks.

[PeWe]

This set has been working OK before to thst engine or another  big bore CB750?

Sudco has recommended settings for VM29 in their catalog.
I guess the needle jet, air jet are OK, pilot 17.5 according to them if I remember correctly when I had it with 836.

Pilot 20 might work too. Main jet around 120-125.

BUT, check if your set is made for Kawasaki, air jet then smaller according to them. 0.6, CB750 0.9.

Good idea to check throttle too. For other bikes different cut out. Needle jet numbers seen when removed.

[Don R]

 Yes, the PO had these carbs on this same engine in the same bike. He just removed them for safe keeping when the bike went to the farm for storage.
  He rode it and drag raced it like this with velocity stacks, not sure if he had filter socks but I didn't get any with the purchase. RC high comp 836, ported, RC315 cam, light retainers and RC springs, RC 4-1 pipe. Gerex ignition, light flywheel. I think the plate is 1987. I think the oil/atf I put in the cylinders wet fouled the plugs.
 
  When the lift is empty, it gets the ignition checked and an 800 watt starter installed.

[Don R]

This is drag bike #3 the red one, the PO said this flywheel means it is the RC engineering 836 with RC steel rods and forged pistons. Ported, SS valves and RC315 cam, retainers and springs. I'm putting a starter on it at least for now, will need a start relay and maybe an entire battery box, The left side cover area was emptied, maybe the Gerex ignition box was in there once.

[PeWe]

How the VM29 carbs are jetted would be interesting

[Terry in Australia]

This is drag bike #3 the red one, the PO said this flywheel means it is the RC engineering 836 with RC steel rods and forged pistons. Ported, SS valves and RC315 cam, retainers and springs. I'm putting a starter on it at least for now, will need a start relay and maybe an entire battery box, The left side cover area was emptied, maybe the Gerex ignition box was in there once.

Does the Gerex ignition actually work without it's black box and special coils Don? It's a multi spark ignition and a pretty expensive unit in it's day, I think Jerry has a NOS one somewhere?

[Jerry Rxman Griffin aka MuthaF'er]

As a matter of fact I do have a NOS NIB Gerex in my parts cave that could use a new home. My take too that they are expensive. Just not sure what the market would bear.

[Terry in Australia]

I’d love one Jerry, but I wouldn’t pay more for one than say, a Dyna 2000 kit, because I think the Dyna 2000 is the best electronic ignition that you can put on a CB750, and a Gerex isn’t as pretty (but works way better than) an ARD magneto, which all the cool kids want. You, me and Don know what a Gerex is and how good they are, but most folks don’t, so they’re not particularly desirable either.

[Don R]

This is drag bike #3 the red one, the PO said this flywheel means it is the RC engineering 836 with RC steel rods and forged pistons. Ported, SS valves and RC315 cam, retainers and springs. I'm putting a starter on it at least for now, will need a start relay and maybe an entire battery box, The left side cover area was emptied, maybe the Gerex ignition box was in there once.

Does the Gerex ignition actually work without it's black box and special coils Don? It's a multi spark ignition and a pretty expensive unit in it's day, I think Jerry has a NOS one somewhere?

 It still has the black box, it's just incorrectly mounted under the oil cooler now. I'm not sure about the special Gerex coils. I'm re-reading the Gerex timing and wiring instructions. I put a starter on the bike (for now) and noticed the neutral detent roller was out of place. While putting it back where it goes I noticed the stud threads are stripped out. This would explain why it popped into gear from N a few times while I was kick starting it. I hope the case just needs a helicoil and isn't cracked. For now I'll stick to trying a startup. I need to hear it run. 

[Don R]

How the VM29 carbs are jetted would be interesting

 I will make a chart of what's in there now.

[Don R]

 It has a starter, start relay for a lawn tractor, borrowed battery, and spins. Makes oil pressure. It has spark on all cylinders and appears to be timed properly but 2-3 sparking are dependent on placement of the sensor cable. Fuel is there, but I suspect I did not do a good enough job cleaning the carbs.
 It wants to start but does not. It's dinner time now, if these carbs come off, they won't go back on.

[Terry in Australia]

That's what I like about Harleys Don, put any carb in any condition on one, and it'll just run. I have no idea why Jap bikes are so finicky.

[Don R]

 I found the falling into gear and odd shift feel problem when I was kick starting it, the neutral detent roller spring was unloaded and on the wrong side of the shift drum. Then while fixing that, I noticed the stud threads in the case are gone. I'm hoping this is all that's wrong and why he stopped riding it.
 I think I have a 6mm helicoil kit.

[Don R]

 It lives! It ran long enough and was loud enough for my wife to hear it in the house. After the baffle fell out. No bolt. Pumps oil and everything. I need to drop the pan, should have done it first.