FRANKENHONDA II the 1982 DOHC CB 750F2 Build

jag767 said:
Trail isn't the problem. His nemesis will be speed bumps, and being stable at 55mph ;D

Don't feel bad, I screwed up a bike so bad I had to cnc a new oil pan, and fab a new exhaust just to have sufficient ground clearance to clear ant hills. It happens lol.
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Yea thats why i need to come up with some way to effectively mount the steering damper... and then spend the rest of my days watching out for speed bumps

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cb250nproject said:
Yea thats why i need to come up with some way to effectively mount the steering damper... and then spend the rest of my days watching out for speed bumps

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Even with a damper 23° is worrysome, that's less than modern sportbikes. Then there's the issue of the added stress to the frame with the new head tube angle.
 
jag767 said:
Even with a damper 23° is worrysome, that's less than modern sportbikes. Then there's the issue of the added stress to the frame with the new head tube angle.
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Devin seemed to give me the impression that there was no issue and that it would improve handling..

has anyone following this thread actually done this conversion? ? I know guys who are in the process of doing this but noone has finished and tested it.

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cb250nproject said:
Devin seemed to give me the impression that there was no issue and that it would improve handling..

has anyone following this thread actually done this conversion? ? I know guys who are in the process of doing this but noone has finished and tested it.

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At low speed, yes. But the faster you go the more twitchy itll be.
 
I haven't messed with this particular swap but I have taken a modern front end and put it on an old motorcycle. Honestly the bike probably handled better before. Now it did well around town but if you really wanted to ride the bike the handling sucked. The bike didn't want to turn, would want to stand up in mid turn, etc. I wound up finding a front end that was a close match with the original equipment and the bike improved. To me, it's not worth going through all this trouble and end up with a bike that may handle worse than it did before.

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clem said:
I haven't messed with this particular swap but I have taken a modern front end and put it on an old motorcycle. Honestly the bike probably handled better before. Now it did well around town but if you really wanted to ride the bike the handling sucked. The bike didn't want to turn, would want to stand up in mid turn, etc. I wound up finding a front end that was a close match with the original equipment and the bike improved. To me, it's not worth going through all this trouble and end up with a bike that may handle worse than it did before.

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With his numbers i'd wager it'd dive into a turn more than anything, but your point is still the same.
 
I guess the proof will be in the pudding, im too far in now to turn back. I've committed to the frobt end conversion and will now have to see it through to fruition. I wish i wasnt away for another 5 weeks i could probably have it just about finished if i had that long to work on it... although that estimation may blow out as i am thinking of redoing the seat pan

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If you go with the stepped triple you should be fine. As well as a steering damper. There are lots of guys who use 17” rims front and back, just go to the cb1100f.net site and you’ll see ton’s of examples. One of the guys sells kits for the conversion to 17” cbr rims. I believe Freddie Spencer had 17” wheels on his bike. Granted he did use stock length forks. I’m not sure of the numbers on the stock forks but I don’t think it’d be more than 2” difference. He definitely had a damper. Also, though I did change the rear suspension on my f, the bike handles very well with the damper. My trail was 4.4” right there with modern sports bikes. If you’re worried about clearance you can switch to a 4-2-1 header and gives you a little more space.
 
You’re right, I went back and checked my numbers. My trail is right about 4. I was thinking of my nighthawk.
 
Ok so some more progress, before I left I had identified that the part of the CR carbs that inserts into the boots was the incorrect external diameter.
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Perhaps they were set up for a SOHC I'm not sure as the seller said they were of a cb 750... Maybe he was just talking theories to sell it.
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I realised that the part in question simply unscrewed

Anyway before I left for work I passed my original carbs and new CRs to my dad, I explained the predicament and asked if he could turn me up some adapters on the lathe to match the external diameter so I could use normal CV boots

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This was his plan

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The smaller one is the original

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He then match ported them so the internal diameter would match the internal ID of the CR s and the ID of the CV boot there was about a 6 mm difference between the two
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This is the first of the four the other three are yet to be made but I'm pretty happy with the way it turned out (no pun intended)

After this the adapter brackets for the rear sets will be made up


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Beautiful machining... your dad is a talented man... is he running CNC or Manual?


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Has anyone on here run the CR 29's on a cb 750 ? im just wondering do i need to change the petcock at all to provide more fuel or is the stock petcock fine ??

I just purchased new CV boots as the rubber had perished on my old ones which were cracked. It's my day off tomorrow Im trying to work out what else is left to purchase.

I know I have to customise the front brake line to allow for the clip on risers, but I will wait until i can take the whole bike to the shop just to ensure the lines sit nicely.

I still need to find some small LED or projector lights to mount into the custom front fairing i want to make.

Still also need to work out what size sprockets front and back will be best
 
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