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What Should I Do?
Keep the K1200S and make it work? 100%  100%  [ 2 ]
Sell the K1200S, and get one of the "normal" BEC engines? 0%  0%  [ 0 ]
Ditch the car and build a locost? 0%  0%  [ 0 ]
Total votes : 2
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PostPosted: March 24, 2021, 7:01 pm 
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Joined: October 10, 2010, 11:07 pm
Posts: 8
Hi,

I am in the midst of "restoring" (meaning, getting it to a roller condition) a 1973 Jensen Healey. The plan all along has been to drop a bike engine in the car. So, I started looking for possible bikes, and came upon an inexpensive K1200S. The K1200S engine in stock form makes about 170 HP, and it has a dry sump oiling system, while the JHs engine makes 130 stock -- a nice bump in power. So I snapped it up.

However, I have been having a difficult time finding some important information about the bike. It is a shaft drive, which I can't decide is good or bad. The following are "doubts" and/or questions I have for the transplant, which I hope some people can chime in on so I don't strip the bike down and end up with headaches.

The differential on the JH is offset several inches to the passenger side, which I think would be advantageous for most BEC installs. However, I can't figure out if I can easily remove the drive shaft components, and use the engine installed in a transverse orientation like a "regular" bike engine in a BEC. If I can, I can't figure out which direction the output shaft rotates, and what options there are to mate the engine to the differential. If it is possible to remove the shaft drive and parts, and the rotation is opposite of the diff, I believe one option is to flip the differential. Wondering if I can flip just the differential, leaving the tubes and axles as is, so the diff remains offset the few inches it currently is. Also, I was considering swapping in a Ford 8.8 rear end. If I go custom size (and I likely would need to) I assume I can offset the diff, perhaps even more, so I can straighten the driveshaft as much as possible.

If I need to keep the shaft drive, I can try and sell the bike and find a more appropriate bike for the engine, or, I can try and mount the engine "in line." But, I think that will cause some serious engineering challenges, since the shaft comes off the drivers side of the bike, and the diff is offset to the passenger side requiring either the engine to be installed all the way to the passenger side shock tower/wheel well, and likely still leave me with poor drive shaft angles, or, flipping the entire rear axle, and hammering out a new drive line path under the car. Or, a custom Ford 8.8.

Finally, gear ratios are super confusing to me. The K1200S transmission has the following ratios:
1. 3,93
2. 2,87
3. 2,27
4. 2,01
5. 1,78
6. 1,582

The drive shaft ratio is 2,82. The JH differential is likely 3.73:1 (There are two different rear ends, depending on year, but owners sometimes changed them). I am looking for brisk acceleration but primarily I don't want to tax the transmission and engine too much, but also don't want to be reving the engine to 10k to maintain 60mph in 6th gear. What do people think of the mix of these parts? Also, what should be the rear end ratio -- if I go Ford 8.8, I will look to get the ratios correct for the application.

Phew, that seems like enough for now.

Thanks to everyone, in advance, for the help and information.


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PostPosted: March 25, 2021, 2:06 am 
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Joined: April 19, 2018, 2:02 am
Posts: 255
Just from looking on the interwebs it looks like the bikes driveshaft spins clockwise viewed from the rear.

I would think that engine is a great choice for a BEC, dry sump and driveshaft seem like huge benefits.

I haven't completed my BEC yet (or a locost) so my experience is limited.

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PostPosted: March 26, 2021, 1:28 pm 
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Joined: December 22, 2006, 2:05 pm
Posts: 8037
Doesn't seem like you've put much thought into this. Considering the vehicles suspension, diff, and brakes, the cost and availability of used bike parts, the Honda v4 shaft drive is the best way to go imho. You could end up butchering the car to make the bmw fit but not be able to justify the cost of eventually repairing it.

Sell bike, sell restored car, build around desired drivetrain.

Pics of the jensen?

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