Topic: 750 @ 1200cc? drag bike how did they start?

[Don R]

I was told the drag bike I made a deal on is 1200cc. The family of the po provided the info. The po was not a BS'er so I think it MIGHT be true. How was this achieved back in the 70/80's? I'm assuming a welded stroker crank and big bore cylinder sleeves that should be visible through the fins. Probably a spacer under the cylinder? What header might be appropriate on a bike of that time period for track use only. They said it was started on power rollers, there is a kicker on the engine but I was told it wouldn't kick over very well. ARD mag for sure.
  We'll see this week if they keep the deal. One of the sons wasn't very thrilled with the idea of selliing it.

[754]

Yes 1080 with stroker.. If its not an RC custom block you should see sleeves.  Be a leaker on the street

[jweeks]

900F crank in place of the stock one. About a 3mm spacer plate under the cylinders for the increased stroke. About a 1180cc motor. Haven't heard of anyone welding up and offset grinding a 900F crank, but it can be done for another 2 - 3mm increase. A stock crank can be reworked for a +5mm stroke increase. RC block would be period correct for a big bore. A few measurements and you'll find it's probably a little smaller than 1200cc.

                                                            Jon Weeks

[Don R]

Thanks, that's what I assumed. I wasn't sure what year the 900's came out but that sounds right. That's a whole lot of sohc 750. He did tell me once he twisted a crank off at the alternator. This bike was once a stock class 750. It ran within .002 of whatever NHRA record there was in the 70's.
I'd like to put it in race condition but no way would I race it. 
 I'm hoping to talk to them again tomorrow.  The fiberglass tank is missing, I'd love to find an old leaker so I could put one on as a shell with small tank inside. 
Would a bike like this just have 4 drag pipes? Hence the name?

[Don R]

What are the methods of starting an engine like this? I was told they used rollers because it couldn't be kicked.

[valt]

Yah, I'm guessing that motor is very high compression. So they would probably have used rollers since the crank side is probably driving some kind of mechanical fuel pump and I right? A lot of racing guys will use a gun on the crank to turn it over, like in moto GP. But if you are running a mechanical fuel pump off the end of the crank, I'm not sure that is possible.

[dragracer]

Outboard starter on the rotor side of the motor. A tapered nut is bolted in place of the rotor. Standard  size of that starter nut is 1 1/8". Have you ever watched the NHRA pro stock bikes get cranked up??

We use them on our dragbikes all the time. Pingel sells them. You will need 2 -12volt batteries hooked up in series to make 24volts. Those batteries and the starter are mounted on a starter cart. You can buy on already done or go the cheaper route like i do and use a modified hand truck. I also make up my own outboard starter using a Toyota V6 gear reduction starter, 84-94. Be sure to get the HD one since it has a bit more horsepower. Weld an 1 1/8" deep wall socket on it, disable to starter bendex from kicking out and your done. Oh, i use 1/0 welding leads and quick disconnects for the battery cables but Pingel sells them fancy stuff already made up.

[dragracer]

Here is a starter cart similar to a Pingel unit. Also an APE outboard starter nut. You would need a flat plate with a crank seal in place of the stock stator cover. I think CYCLEX has both of the later parts for an SOHC

[dragracer]

Starter plate from cycleexchange with seal.

[Medyo Bastos]

I have a set of stock jugs with 73mm sleeves that I wont be using. 

[Don R]

Outboard starter on the rotor side of the motor. A tapered nut is bolted in place of the rotor. Standard  size of that starter nut is 1 1/8". Have you ever watched the NHRA pro stock bikes get cranked up??

We use them on our dragbikes all the time. Pingel sells them. You will need 2 -12volt batteries hooked up in series to make 24volts. Those batteries and the starter are mounted on a starter cart. You can buy on already done or go the cheaper route like i do and use a modified hand truck. I also make up my own outboard starter using a Toyota V6 gear reduction starter, 84-94. Be sure to get the HD one since it has a bit more horsepower. Weld an 1 1/8" deep wall socket on it, disable to starter bendex from kicking out and your done. Oh, i use 1/0 welding leads and quick disconnects for the battery cables but Pingel sells them fancy stuff already made up.

I see the current bike guys start at the track, I was wondering about back in the day, I don't remember rollers at the track, aI don't see a starter drive on this bike, the kids said their dads bike won't kick een though start the kicker is there.  I was wondering about getting it in starting/running condition but I don't want to race it.

Thanks for the parts breakdown, that is the best way for me if this project goes foreward.

[Jerry Rxman Griffin aka MuthaF'er]

Hey Don, just have Bud bump start you    . Find a kid to try it. I'm not sure if I'd want to try a kick starter with that engine. My leg is just now healing good from the 2 broken bones.....

[dragracer]

Outboard starter on the rotor side of the motor. A tapered nut is bolted in place of the rotor. Standard  size of that starter nut is 1 1/8". Have you ever watched the NHRA pro stock bikes get cranked up??

We use them on our dragbikes all the time. Pingel sells them. You will need 2 -12volt batteries hooked up in series to make 24volts. Those batteries and the starter are mounted on a starter cart. You can buy on already done or go the cheaper route like i do and use a modified hand truck. I also make up my own outboard starter using a Toyota V6 gear reduction starter, 84-94. Be sure to get the HD one since it has a bit more horsepower. Weld an 1 1/8" deep wall socket on it, disable to starter bendex from kicking out and your done. Oh, i use 1/0 welding leads and quick disconnects for the battery cables but Pingel sells them fancy stuff already made up.

I see the current bike guys start at the track, I was wondering about back in the day, I don't remember rollers at the track, aI don't see a starter drive on this bike, the kids said their dads bike won't kick een though start the kicker is there.  I was wondering about getting it in starting/running condition but I don't want to race it.

Thanks for the parts breakdown, that is the best way for me if this project goes foreward.

Any chance you could post pics of both sides of the engine so we can study it???

[Don R]

I got a good look at the bike, no cylinder spacer, no sleeve through the fins. It's hard to tell a guy he might not have what his dad said was there. I bought it anyway. The kicker is broken. The engine turns free.
 I paid too much but they want it restored and then buy it back OK we'll see. It needs to start even if it's another engine.

[Don R]

Any chance you could post pics of both sides of the engine so we can study it???
[/quote]

The points end has the ARD and the dyno end is an empty case with the crank end and a bolt in it. Apparently they roller started it. I wasn't racing back then and don't really remember the rollers at the track.

[754]

Search okeefe ranch July 7.  Video by Jean Beauregard.. I think it shows the roller we used. I cant view it so not sure..