FRANKENHONDA II the 1982 DOHC CB 750F2 Build
- Thread starter cb250nproject
- Start date
cb250nproject
If you can make it better do so
Then as I was traveling home through slow traffic it stalled and would not start, I had gassed on then jumped on the breaks, then conked out.
I was on the inside lane of a 4 lane bridge, luckily I was on the down hill side so I rolled across 4 lanes and exited on the slip and rolled it up on to the foot path.
I tried starting it in second while rolling down hill nothing.
Then after 15-20 starts then rides home no drama
The head gasket and tacho seals are still leaking, I’m thinking I’m going to need to bite the bullet and take the engine out and do it all over again and get it right. Boooo better to suffer the pain now and have a motor that will last another 20 years.
Also I can’t tell if it’s normal or not but it feels like it bounces or something in the front end it’s really hard to explain, I might take the R1 out for comparison to see if it’s just new fork or what.
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cb250nproject
If you can make it better do so
I noticed the #3 spark plug lead had a cut in it so I changed that out.
While I was at it I removed the cam cover and cleaned it and the cam cover seal. All the little rubber seals around the cam cover bolts are shot and it’s Leaking around the cam cover and tacho seal again :/
I’ll wait until tomorrow and fix Rex a call to see if he can get me a new copper head gasket or maybe how much he will charge to put one in, and also why the bike would have just cut out the other day. I was driving through slow traffic, gave it a blip on the throttle, hard on the brakes then it stalled and wouldn’t start for 15-20 minutes, then started and ran no issues.
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cb250nproject
If you can make it better do so
Well today was the day, OMM came over and we pulled the motor out View attachment 220887View attachment 220888
I taped up the frame and put some rags in place after I had removed the carbs, and disconnected all the wiring, starter motor and chain sprocket ready for OMM to arrive.
Once he came over we made short work of removing the motor, unfortunately it because of how much practice we have had. View attachment 220889
We put the motor into the stand that I had cobbled together from the first time the motor was out
or was it the second, or third, fourth, fifth ? I lose count now.
View attachment 220890
Anyway with the motor out we got the cylinder head off without too much trouble, to my surprise the gasket looked like it was in really good condition, we then removed the gasket which came off without too much trouble.
View attachment 220891
I inspected the top of the cylinders on the side where the leak was, and other than finding all the Honda bond I had put there in an attempt to fix it there was nothing I could see that would have made it leak, even the underside of the gasket was in good nick.
View attachment 220892
Next I cleaned the surface with grease remover and cleaned them up before sliding the head back on.
View attachment 220893
You can see where we made a dummy cam to hold the shims in place, I think I would have had a break down if I had to do that all over again.
I torqued the head bolts down in sequence first to half torque then 30ft lbs one over but Rex said that’s ok, the proof will be in the pudding
View attachment 220894View attachment 220895
Reconnected the oil delivery line and got the last two crankcase bolts in that are on top of the oil filter
I still have these two bolts left from my kit and I can’t for the life of me work out where they go. Maybe Jimbo can help me out here ??
Next we turned the motor to TDC 1.4 and lined the cams up, first attempt both were out by one tooth but we got it spot on.
We were in the home straight we put all the cam journals on and were just torquing them down I started to torque up the first bolt, and it spun, and spun, and spun
no fu€king way
Yep it’s halicoil time... unfortunately it was too late in the day to go get one so that’s where today’s instalment ends.
Tomorrow I’ll get a halicoil kit x 3 just encase and I’ll get this all buttoned up and maybe even get it back in and for a leak free ride, fingers crossed
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I taped up the frame and put some rags in place after I had removed the carbs, and disconnected all the wiring, starter motor and chain sprocket ready for OMM to arrive.
Once he came over we made short work of removing the motor, unfortunately it because of how much practice we have had. View attachment 220889
We put the motor into the stand that I had cobbled together from the first time the motor was out
or was it the second, or third, fourth, fifth ? I lose count now. View attachment 220890
Anyway with the motor out we got the cylinder head off without too much trouble, to my surprise the gasket looked like it was in really good condition, we then removed the gasket which came off without too much trouble.
View attachment 220891
I inspected the top of the cylinders on the side where the leak was, and other than finding all the Honda bond I had put there in an attempt to fix it there was nothing I could see that would have made it leak, even the underside of the gasket was in good nick.
View attachment 220892
Next I cleaned the surface with grease remover and cleaned them up before sliding the head back on.
View attachment 220893
You can see where we made a dummy cam to hold the shims in place, I think I would have had a break down if I had to do that all over again.
I torqued the head bolts down in sequence first to half torque then 30ft lbs one over but Rex said that’s ok, the proof will be in the pudding
View attachment 220894View attachment 220895
Reconnected the oil delivery line and got the last two crankcase bolts in that are on top of the oil filter
I still have these two bolts left from my kit and I can’t for the life of me work out where they go. Maybe Jimbo can help me out here ??
Next we turned the motor to TDC 1.4 and lined the cams up, first attempt both were out by one tooth but we got it spot on.
We were in the home straight we put all the cam journals on and were just torquing them down I started to torque up the first bolt, and it spun, and spun, and spun
no fu€king way Yep it’s halicoil time... unfortunately it was too late in the day to go get one so that’s where today’s instalment ends.
Tomorrow I’ll get a halicoil kit x 3 just encase and I’ll get this all buttoned up and maybe even get it back in and for a leak free ride, fingers crossed
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^^ that's a good suggestion. It might also be worth checking (although now I guess you've already re-assembled the engine) that there was no crap in the dowel pin locator hole which could cause the dowel pin to not seat entirely? Just a suggestion.
Not 100% sure about those two long bolts you've got left over. All the bolts should have been bagged separately for each individual location (clutch cover, oil pan etc). Could they be for the starter motor cover?
Bummer on the cam holder bolt - I had to helicoil a couple of threads in the cam holders themselves, where the valve cover bolts thread into. Helicoils man...lifesavers.
Not 100% sure about those two long bolts you've got left over. All the bolts should have been bagged separately for each individual location (clutch cover, oil pan etc). Could they be for the starter motor cover?
Bummer on the cam holder bolt - I had to helicoil a couple of threads in the cam holders themselves, where the valve cover bolts thread into. Helicoils man...lifesavers.
Last edited:
cb250nproject
If you can make it better do so
cb250nproject
If you can make it better do so
Well I halicoiled one hole successfully, but I’ve identified another 3 that I need to fix. I’ve had to call stumps because I’m of yours work in Tassy for a week so I’ll luck up where I left next Saturday, if all goes well (famous last words) may even get a leak free test ride in
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cb250nproject
If you can make it better do so
So it’s been a while and while the head is at T. rex racing getting halo coils put in I’ve turned my attention to the rear set adapters as Rex said the rear sets sat too high.
I’ve just made up a template that I will take to OMM so we can look at knocking over the last few items from Rexs’ punch list
I’ve also decided that I am going to install an oil cooling system. This will involve replacing the oil pump with one from a Cb 900, modifying the sump to match a Cb 900 sump. Rex was good enough to send me home with a spare sump he had so we could use it as a template to go by
The sump is with OMM and once he has worked out how he is going to secure it to the mill we will be away.
I have found these connections on eBay, they’re exy but will allow me to run modern non OEM hoses.
After talking with Rex he convinced me that the OEM 900 oil cooler is not much chop, and advised me to look at a more modern option. I’m thinking as long as it is black I should be all good.
All because of some weeping gasket, it’s become a 1 step forward, 3 steps back situation, should make riding it all the more sweeter I guess.
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I’ve just made up a template that I will take to OMM so we can look at knocking over the last few items from Rexs’ punch list
I’ve also decided that I am going to install an oil cooling system. This will involve replacing the oil pump with one from a Cb 900, modifying the sump to match a Cb 900 sump. Rex was good enough to send me home with a spare sump he had so we could use it as a template to go by
The sump is with OMM and once he has worked out how he is going to secure it to the mill we will be away.
I have found these connections on eBay, they’re exy but will allow me to run modern non OEM hoses.
After talking with Rex he convinced me that the OEM 900 oil cooler is not much chop, and advised me to look at a more modern option. I’m thinking as long as it is black I should be all good.
All because of some weeping gasket, it’s become a 1 step forward, 3 steps back situation, should make riding it all the more sweeter I guess.
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cb250nproject
If you can make it better do so
So I picked up the head today from Rex, he fixed up the damaged holes and gave me Honda bolts which went a little deeper than the ones I had
In addition he linished the grooves of the cam tensioner and mad a spacer to adjust the height
We spoke about using a little sealant on the head gasket, and he showed me which one to get.
Unfortunately when I went around the corner to pick up a new head gasket I realised the shop is closed on a Monday. So hopefully tomorrow they have one in stock and I can go pick it up and start putting this back together.
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In addition he linished the grooves of the cam tensioner and mad a spacer to adjust the height
We spoke about using a little sealant on the head gasket, and he showed me which one to get.
Unfortunately when I went around the corner to pick up a new head gasket I realised the shop is closed on a Monday. So hopefully tomorrow they have one in stock and I can go pick it up and start putting this back together.
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cb250nproject
If you can make it better do so
Fingers crossed, I’m just waiting on the spares shop to confirm they have the head gasket so I can start to slowly and methodically put her all back together again so it’s all good.
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cb250nproject
If you can make it better do so
Thanks Pete, I picked up the head gasket yesterday, so hopefully after a bit of running around today I’ll get some time to piece her back together.
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cb250nproject
If you can make it better do so
Yep I actually hit both dowels with the file just to be sure 
OMM asked the same thing
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cb250nproject
If you can make it better do so
Ok, so got some shed time, and it’s not been without Murphy’s law rear it’s head a few times.
I cleaned up the cylinder surface
As per Rex’s instructions I used a small amount of three bond 1211 on the head gasket
( the pink string is attached to a magnet that I use to retrieve the cam chain, note: string must be pink)
This time I made sure all the cam tensioners were in place before putting the head back on. It actually went on pretty smoothly, first I torqued the cylinder head nuts down to 15 ft lbs then 30 ft lbs.
cam chains in but not before I put the inlet cam in a full 180 degrees out in my defence the previous day I thought it would be a good idea to run a half marathon ( I’m not the half marathon type) and then before working on the bike it took jnr out on the bike for a two hour ride so I was a little fatigued but wanted it done ( in hindsight it was a stupid idea)
So with the inlet cam in incorrectly I turned the motor by hand, luckily one of the exhaust shims on cylinder one dislodged some how and stopped me turning. When I looked at that I noticed that I had put the cam in incorrectly.
So after cursing myself a number of times I undid what I had done and replaced the cam correctly. In addition I had to put a washer underneath the b cam tensioner.
So once it was all buttoned up I turned the motor over and over watching the the buckets and shims to make sure they were following the cam lobes and not sticking.
Now I’m going to have to wait until the motor is in to do a compression test, so I can be 100% that everything is as it should be.
I managed to find some second hand hoses from a Cb 900 and I think OMM will get a chance to drill out the sump. Once I have the fittings I’ll go back to Rex and see what we can do about magyvering something that’s looks half descent.
Here’s to hoping I haven’t bent valves
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I cleaned up the cylinder surface
As per Rex’s instructions I used a small amount of three bond 1211 on the head gasket
This time I made sure all the cam tensioners were in place before putting the head back on. It actually went on pretty smoothly, first I torqued the cylinder head nuts down to 15 ft lbs then 30 ft lbs.
in my defence the previous day I thought it would be a good idea to run a half marathon ( I’m not the half marathon type) and then before working on the bike it took jnr out on the bike for a two hour ride so I was a little fatigued but wanted it done ( in hindsight it was a stupid idea) So with the inlet cam in incorrectly I turned the motor by hand, luckily one of the exhaust shims on cylinder one dislodged some how and stopped me turning. When I looked at that I noticed that I had put the cam in incorrectly.
So after cursing myself a number of times I undid what I had done and replaced the cam correctly. In addition I had to put a washer underneath the b cam tensioner.
So once it was all buttoned up I turned the motor over and over watching the the buckets and shims to make sure they were following the cam lobes and not sticking.
Now I’m going to have to wait until the motor is in to do a compression test, so I can be 100% that everything is as it should be.
I managed to find some second hand hoses from a Cb 900 and I think OMM will get a chance to drill out the sump. Once I have the fittings I’ll go back to Rex and see what we can do about magyvering something that’s looks half descent.
Here’s to hoping I haven’t bent valves
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