FRANKENHONDA II the 1982 DOHC CB 750F2 Build

Avvatar

Member
Those CRs look beautiful on the clean engine. This whole bike is shaping up beautifully. Glad to hear the OMM adapters did the trick and heating the carb boots is a nifty trick to keep up my sleeve.
 

cb250nproject

If you can make it better do so
https://youtu.be/5fY23FeBGpw

This just happened pretty dam happy, she must be running super rich went through about 400ml of fuel in that short time and blew some black smoke


Sent from my iPhone using DO THE TON
 

cb250nproject

If you can make it better do so
Ok I’m off the high now,

So before this epoch moment occurred I was hooking up everything, I must have reset the m unit or something as the headlight settings changed and the bike didn’t want to start, upon investigation I think it may be dodgy connections on the starter solenoid.

Anyway I took all the spark plugs out and poured a little oil into each cylinder, then let the engine crank for a bit just to get the oil to the top of the motor. Then I put all the plugs back in and hooked up my water bottle fuel tank and hit the start button. It cranked for about 30 seconds no joy before the fuel bottle fell off its perch. I picked it back up put the choke on full then bam a little magic happened. Tomorrow I will complete the rest of the wiring and put the lithium battery back in its place.

Currently I have the battery charging on my new Harley battery charger.

It was quiet difficult to find a lithium safe charger, some guys at the auto shop were trying to tell me that a lead acid battery charger would be fine. Clearly they had no idea. So finally my search took me to the Harley store


Sent from my iPhone using DO THE TON
 

Attachments

Jimbonaut

Well-Known Member
DTT SUPPORTER
Mate is that the first time you fired the bike up in two years? No wonder you freaked the f*ck out - you can't beat that feeling. Great job, hope you're knees in the breeze in no time.
 

cb250nproject

If you can make it better do so
So I've started torquing all the bolts to spec, unfortunately I misread the specs on the front engine mounts over tightened and broke the bolts, so after a few expletives i managed to get the brackets off and the broken bolts out then I went off to get some new replacement bolts before continuing on with torquing all the frame, engine mounts and suspension it's all done now except for the rear axle.

I have a new chain but I'm trying to determine the correct amount of links to have in the chain, front sprocket is 18 teeth and the rear is 40 teeth distance between sprockets is 59.5 maybe 60 cm. i found this site https://www.rbracing-rsr.com/chainlength.html tells me 104.9 which would round up to 106 links, one of the guys on the FB page says 108 although I'm not sure what manual he has (it's definitely better than my Haynes one)

So on the carbs I've found the CR main Jet is 110 and the Main air jet is 240 i didn't check the slow jet, what I'm finding is the bike starts on full choke but and idles higher than 2000 rpm then without choke dies out. (I'm thinking initially I will just adjust the idle screw just so it doesn't stall and I can ride it to a mechanic to do the final tuning).

I didn't put the lithium battery in because I was messing around with starting the motor and didn't want to flatten the battery while i dicked around. Tomorrow I'll bite the bullet with the chain and maybe get the front brake fluid done.
 

Attachments

pidjones

Well-Known Member
My '79 CB750F (stock CV carbs) had to have choke to start cold, and took a loooong time to warm enough to get fully off the choke and not stall at idle. I was told air leak, but check several times with carb cleaner spray and propane with no indications. It got better over time, and balancing definitely helped. When I sold it, it started right up (with choke) after a week-long setting and idled well after warm-up including while loading on their trailer. One thing I'm sure happens is that any oil/cleaner etc. residue left in the system gets washed into the carbs and has to be run out. My GL1000 is still improving after ~400 miles and a year (been mainly showing it this summer).
 

cb250nproject

If you can make it better do so
Hopefully that’s just it with the idle just needs to warm up, I will give it to a professional to tune I just need to be able to get it there albeit a rough ride.

So I managed to shorten and connect the throttle cables all seems to work as it should.

The next thing is did was get some fluid in the new lines of the front breaks. Happy to say I will now be able to stop.

I still haven’t gotten the rear brake line fixed up yet, I’ll probably have to wait until Monday to get that done.

Picked up some missing bolts and installed them, hopefully nothing bad has happened due to my initial omission.

I also realised I need to make up some sort of plug for the hole that the tacho cable use to come out of so oil doesn’t leak out of there (not a cool look)



Sent from my iPhone using DO THE TON
 

Attachments

I think you should take the end of your tach cable over to OMM's shed and see what happens.
Or drill out the cable, tap it and run in a machine screw with some Loctite.
 

teazer

Well-Known Member
DTT BOTM WINNER
Does CrazyPJ offer a blank off plug for the DOHC tacho drive? I would be surprised if one of his twin model plugs wouldn't work in that application.
 

cb250nproject

If you can make it better do so
I actually found the old tacho cable so before I order something I’m going to see what I can Magyver up


Sent from my iPhone using DO THE TON
 

cb250nproject

If you can make it better do so
I think using only a can of hairspray and a sparkler magyver would have done a nicer welding job.

Oh well it will hold until I can get to the OMM workshop and have a go on the lathe.

Rear brake reservoir is in place and plumbed into the rear brake piston, had the rear brake like made shorter and that’s all connected in.

I think I have an air lock in the lines as it’s proving difficult to bleed out may have to take the caliper off and lower it below the master cylinder and clamp it onto an old disc I have.

I’ve also found that the throttle cables are sticking, there is going to be a little reworking here... I have some new cables I might run through as I simply shortened the old cables last time.

Oh well if at first you don’t succeed, try and try and try .... and try again


Sent from my iPhone using DO THE TON
 

Attachments

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom