FRANKENHONDA II the 1982 DOHC CB 750F2 Build

Nybz said:
I am sure you got it but, when putting the cylinder back on, make sure that A cam chain tensioner is in there....it can be a common mistake, don’t ask how I know

Does the 1982 have o rings on the back studs, like the earlier models?

Sorry to hear about the broken ring
Sucks to be waiting all that time to build the engine and this happens. Keep up the awesome work, looking great!

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i reckon they do Ive found 4 o rings which seem to correspond with the extra space at the back of the gasket on the inner 4 studs
 
Nybz said:
Glad ya found it before buttoning up the head


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I actually had two gasket kits in the garage and used another two so that all the rear bolts had one, made more sense as when you look at the underside of the head there was a place for a seal on all of them.

Just before I put the cylinders on I realised I’d missed another seal the one, that goes around the base of each cylinder , lucky I didn’t do any work to the gearbox I may have really screwed something up.

The seals were baked into position I was struggling to get them out, then the wifey saw I was having trouble and gave me a pick she uses for sewing worked a treat.

So just by chance when I was returning my shims to Ken Colvin I thought I’d try my luck and see if he had the piston ring kit I was waiting for. He pulled a rabbit out of a hat and with that I returned to the shed armed with the part I needed to put the engine back together

With the hours of my last day off quickly running out. I went to the garage put the gasket that sits in between the gearbox and the underside of the cylinders together with the O rings 6 of ;). Then together with my wife we slowly manoeuvred th cylinders down over each piston, compressing each ring as we moved down which is a lot trickier than it sounds.

Next job was the installation of the cam tensioners into the head.

Disclaimer it was at this point in time I may have deviated from best practice. Now the instructions say to remove the valves, springs and buckets prior to grinding out enough space to house the B cam tensioner

I lacked the skills, tools and time to do this. So I did the next best thing, I got my 100 mile an hour tape and some paper towel and I taped that sucker up. I then got my vacuum and dremel and went to work.

After going through all my bits and with the hours running out I ended up finishing the last part with a chisel (talk about wrong tool for the job) but it produced the desired effect) and the B cam tensioner fit.

I also had to shave a little of to house the curved guide also, once that was completed I removed the cam journals and cams then tightened down the head bolts. By this time it was about 10 pm, the garage was a mess and I hadn’t packed for fly out today so I called it.

Packed everything up waiting for my return in 6 weeks time. It’s just installation of the cams, timing and we may be in with a real chance to start this sucker next break.

Also I picked up the top triple from OMM’s garage and did a test fit. So the gsxr forks have a thin cap that goes over the head stem top bearing. But the Cb 750 runs a thicker one so this created a clearance issue. So in true Frankenhonda form there will be another reiteration we will need to make up a top bearing cover then most likely remove the boss from the underside of the triple this will allow the top triple clamp to sit lower so the nut does all the way up on the stem.


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We gotta wait 6 weeks for more updates? 6 weeks??? ;)

You've got the patience of a saint my man. That top triple's gonna look the part alright, everything coming together very nicely indeed. Can't remember - is your OEM overhead cam chain tensioner busted? I'm on the lookout for one...
 
Jimbonaut said:
We gotta wait 6 weeks for more updates? 6 weeks??? ;)

You've got the patience of a saint my man. That top triple's gonna look the part alright, everything coming together very nicely indeed. Can't remember - is your OEM overhead cam chain tensioner busted? I'm on the lookout for one...

Lol I’ve made so many mistakes through my impatience as a result I’m slowly becoming more patient.

That said I do really want to hear it run next break

The tensioners were cracked and worn, one was not too bad but I can’t remember which one it was. When I get back home I’ll take photos to show you.


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Cool, thanks mate. It's the overhead tensioner I'm on the hunt for. I did get in touch with the guy in NZ and inquired about his upgraded versions - if I had the scratch I'd plump for them instead.
 
Jimbonaut said:
Cool, thanks mate. It's the overhead tensioner I'm on the hunt for. I did get in touch with the guy in NZ and inquired about his upgraded versions - if I had the scratch I'd plump for them instead.

It’s exy but I’m already balls deep, I use to run a spreadsheet to track the cost of the build. I scrapped that long ago, like I keep telling the wifey you can’t put a price on happiness.


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cb250nproject said:
It’s exy but I’m already balls deep, I use to run a spreadsheet to track the cost of the build. I scrapped that long ago, like I keep telling the wifey you can’t put a price on happiness.
Amen to that. Missus bought a bunch of pricey face cream - turns out the credit card isn't just for bike parts after all. Who knew?
 
Hey Jimbo

I found these photos of the cam tensioners I'm not sure how helpful they are, ill get you some better ones once I'm back home
 

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Hey man appreciate the photos - mine's in pretty much the same state. Thanks though - I'll keep my eyes open. Hope the next 6 weeks flies by man
 
so as i sit here in camp with an ocean in between myself and the garage I'm beginning to ponder rear suspension options.

I currently have Hagons they are approx 365 mm (close to stock length i believe) this coupled together with the GSXR forks and 17" tyres front and rear makes the bike sit low. So low in fact i reckon its going to scrape a hell of a lot.

I wonder if anyone else here has done the same conversion because I want to find out what length of rear suspension others are running. I am probably getting ahead of myself but I have nothing else to do for the next 40 days.

so I've been told; your base set-up (for all) is the swing arm is 12 degree (max) drop at full extension (off the ground) and you should be around 20 -25mm sag (bike on the ground).

So I understand sag and I'm assuming that the 12 degrees is how much the swing arm moves down from its horizontal position as you lift the rear up.

I've seen fork extension kits this would raise up the front then allow for taller rear suspension. Vince Hyde actually change the suspension mounting points on the rear which lay them over more (I am beyond the time where that's an option as the frames already been powder coated).

the rake and trail currently is very close to stock if i did extend the forks a fraction i could probably get it spot on to original rake and trail. think there will be some serious R & D this swing. the ohlins option for rear shocks is exactly the same as the ones that are currently on the only difference would be the quality and amount of adjustment available.
 
12 degrees is a lot of droop angle at teh rear which would get worse with longer shocks and/or fork extensions. That said, I'd start by raising the front end with fork extenders or gull wing top triple clamp from say a 929 pr 954. Then work out what you need to do at the rear.
 
teazer said:
12 degrees is a lot of droop angle at teh rear which would get worse with longer shocks and/or fork extensions. That said, I'd start by raising the front end with fork extenders or gull wing top triple clamp from say a 929 pr 954. Then work out what you need to do at the rear.

That came from Brent Hyde about the 12 degrees, but they have a completely different set up with custom mounts on their bikes. Although I would love to jump further into the custom abyss I do want to ride it some time soon.

Has anyone here used fork extenders the ones that screw into the end of the forks ?


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swingarm angle is also dependant on front height, so you need to know fork length or even lower frame rail angle.

lower frame rail angle would give you an absolute frame setting, then you will know what front height you need if you have a 12 degree down swingarm.
 
cb250nproject said:
Has anyone here used fork extenders the ones that screw into the end of the forks ?


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I wish I had a pic of just the extender, but that is what I have here on my BMW R100/7...

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irk miller said:
I wish I had a pic of just the extender, but that is what I have here on my BMW R100/7...
OMM should be able to make you a set of them Phillip, piece of cake.
 
look kinda like these

https://www.ebay.com/itm/Motorcycle-39mm-Stainless-Fork-Tube-Extension-Kit-For-Harley-Dyna-Sportster-XL/202605019059?epid=3029581892&hash=item2f2c333fb3:g:1DgAAOSwaEZcb7Zv
 
Mine are more in depth than that, since they’re TL1000R forks. I found some pics. Don’t mind the rust on the cap screws. Drain holes and the black delrin caps have resolved that issue.



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