Topic: CB750 F1 Restoration Project - not for the faint hearted

[eddiebpool]

Thanks Hondaman, much appreciated.  One wee tip I forgot to mention.  The VHT instructions mention 2x light coats followed by 1x medium.  To get the finish I got I did a very light dust coat from a fresh can at the end.  It really makes a difference.  Simply hold the can a little further away and spray like you are doing a tack coat.  It helps to give the cast aluminium look (if that is what you want).

[eddiebpool]

I haven't posted for a while though I have been busy.  The engine is finally complete (almost).  I still have to do the clutch but that's next on the list.  I decided to paint the valve cover instead of polish.  I'm going to pick up some new tappet covers and polish them, that'll be enough bling for the top.  I couldn't find my old tappet covers.  I may have thrown them away because I remember them being beat up and ugly.  The points cover in the pic is the old one, I put that on because I'll be dropping the engine on that side. (no sense marking up a new shiny one). 

It went together surprisingly well.  The chap that does Hackaweek is a visitor to this site and I wanted his videos more than a few times.  It took several weekends and I really took my time.  Just a few issues

-  I ordered the wrong piston rings.  I didn't realise the F1 had two different pistons.  Mine are the later ones, which I think are the same as the K7.  I'm just the wrong side of the line.  Lesson learned.

-  A couple of the bolts that hold the cam towers to the cylinder head torn their threads.  I pondered trying longer bolts but decided to helicoil instead.  Helicoil is cheap, easy, and definitely stronger than the original thread.  I alway build up my torque and they were all good to 7 ft lb but two tore at 9 ft lb.  After the helicoil and took them all to 8 and no more.

- As mentioned, I decided to paint rather than polish the valve cover.  I had two valve covers to choose from but neither were good enough to polish.  My polishing skills are pretty good but there are dings and deep scratches that will never polishing out.  The VHT cast aluminium paint has a fair bit of sparkle to it in the sunlight, and some polished bolts and polished tappet covers will hopefully complete the look.  I will try to source a good valve cover in the next couple of weeks.  If no luck, it is going in the frame as is. 

I have been doing lots of other little jobs and, once the engine is in the frame, it should all come together very quickly.  I'm thinking I'm 4wks away from completion.  My exhaust is solid but pitted.  I'm going to use it for the moment and maybe get a new one in the spring.  Some of my other chrome is not too hot too.  My thoughts are put the bike together so it is usable, then replace as I source suitable replacements.  More of an issue is my seat pan - rotten and falling apart!  I need to source a new one. 

I've still to do my master cylinder rebuilds.  Tank, side panels and cowl need painted too.  Still a few jobs, but the end is in sight!

[eddiebpool]

Progress being made, finally got the engine in the frame and it should come together quickly now.  I still haven't done my master cylinder rebuilds but apart from that I'm ready to throw everything together.  My tank and seat need work but they will be the last to go on anyway.

Quick query for anyone with experience of rebuilding an F1 / F2 seat.  There are small rivet clips on the inside that hold the colour strips on.  The clips were destroyed in the removal (mostly rotten anyway) but I can't find them anywhere.  I am toying with the idea of getting a cheap tap and die set and putting a thread on the rivets.  It's not the maddest idea I ever had (at least, I don't think so).  I'm thinking there must be a suitably big headed screw out there that would work but can't find what I need.   Any suggestions would be much appreciate.

[eddiebpool]

There is a 10mm bolt hole near the points cover that doesn't have a bolt in it and the diagrams online don't tell you what should be there.  I don't know how essential it is but I have a bolt the right length and I'm tempted to put it in with a nut and washer and torque it down.  I'm assuming it is go give extra support to the cases at that point.  Is it optional?  Any ideas?

One more thing, my bike is lovely and shiny but the the plastic parts (inner rear fender, tool box, air box, etc) are dull.  Has anyone any experience with polishing black plastic?  I'm handy with a bench grinder and buffing but I'm guessing my mops and compounds are doing to be too much for the job.  Any advice on how to get old black plastic looking new would be much appreciated.

[eddiebpool]

It has been a few moons since I have worked on the bike.  Life gets in the way, and Winter is cold in Scotland!  Anyway, Spring has arrived and the Easter holidays start tomorrow.

I've added a pic of the K&N filters on the engine.  I was worried they might look a bit "Cafe" but they really don't.  I think they look excellent and should, I hope, perform better than the stock airbox.  I've upgraded the jets to 115s to take account of the improved airflow.  115 was just a guess and I may have to make further tweaks.  I read the F1s were set up originally to run a little lean.  I'm looking for a nice healthy mix.  If anyone has any ideas on this that would be much appreciated.

The plan is to get the wiring in, test fire the ignition system, then all being well feed the old girl some fuel and see what happens.  Next week - fingers crossed.

[Jerry Rxman Griffin aka MuthaF'er]

Looking good! Keep at it.

Can you pass along the K & N filter part number?

[eddiebpool]

Thanks Jerry

The Filters are K&N RC-2240.  They fit just right with about 1mm gap in between.  The trick to putting them on is a little bit of grease to help them along.  Squeeze / wriggle the filter on to the outside carb (1 or 4).  Once it is on, it should pop onto it's neighbour.  It does need the smear of grease though - too right otherwise and you might damage the filter if you force it too much.

I've read that pods are a pain to set up right.  My thinking is the 4 into 2 K&N offers a shared resource like the stock airbox (avoiding the single pod issues), but better airflow - and they look sweet too. 

I'll let you know how it runs. 

[eddiebpool]

I've not posted for a while though this summer I have been much more active.  I was slowed down considerably by getting an email from the people I bought the cam chain tensioner set from to say the rubber used was dodgy.  They were kind enough to refund the money but didn't send anyone round to do the engine rebuild for me!  I had to tear down and start again, but glad I did so.  I was able to check a couple of things that were on my mind at the same time so not a total waste of time.  So, the build started again and I finally got the old girl started today:

I forgot I hadn't picked a final route for the clutch cable (any suggestions much appreciated) and melted it on the exhaust!  I also realised I hadn't set the cam chain tensioner so that was one rattle I had to deal with.  Brakes need done front and rear.  Just picked up a mini honing tool to clean up the insides of the masters.  I'm hoping the rear will be easy.  The front is proving troublesome.  Two questions I hope people can help me with:

1)  Front brake caliper won't seal between the caliper and hard pipe.  The flare at the end becomes crooked and I can't work out why.  It looks fine inside.  The screw in part doesn't look like it is going in straight but the seems to follow the threads fine.  I'm not sure if I'm dealing with a cowboy repair from the past.  This is the original caliper body.  I have made up a few double flares (done it from cars in the past so know what I'm doing) and every one of them suffers the same fate.  Do I need a new caliper body?  Will that sort the issue?  I'm out of ideas and didn't want to buy a new body to find the same problem.

2)  I had to shorten the return throttle cable because it was around 3 inches too long.  The pull cable was fine for length.  These are after market cables and I heard it is normal for them to be iffy lengths.  The return doesn't seem to do much and the carbs open and close perfectly well without it.  I shortened it and added anyway.  Throttle seems to come on very quickly.  I barely get the handle moving and it is revving up, and just add a bit of pressure and it is starting to tickle up.  I don't remember my smaller bikes being so quick to rev.  Is this normal?  I'm hoping I've done such a lovely job that the carbs are dialled in sweet.  I'm more inclined to believed I made a mess somewhere.

It wasn't a difficult job to shorten the cable.  The hard part, believe it or not, was drilling the wee barrel part to accept the shortened cable.  I blunted two HSS drill bits and gave up on them.  A titanium bit soon got through it but not straight.  I had to then get the hobby tool with a diamond ball bit to clear a central path.  Bit of soldering, tidy it up with a file, and I was done.  There are some excellent Youtube videos that show you the principles.

I need to paint the tank and the cowl.  Side panels and tank flap are done for base coat but awaiting a clear coat to finish (did those with a rattle can).  I've ordered a new spray gun for the job.  My compressor is not big (2.5HP and 50L) so I've opted for an 1.3mm LVLP gun.  Never used one before so will do a bit of experimentation before doing the important stuff.  The bike was originally red but I'm going yellow, very 1970's!

[eddiebpool]

Rebuilt my rear brake master and very happy with the result, and saved money too.  Rear master cylinder kits are expensive.  The hardware was OK and it was only seals requiring changing.  I read somewhere that the seals in after market front master kits are the same.  Just so happens I had one of those!

I was going to rebuild my front master but my front had a deep score in the bore (caused by me trying to get a rusty piston out).  I took the path of least resistance and got a ready built master from David Silver.  It is an after market job, not exactly the same in appearance, but I popped an original cap on it and it looks good.

Preparation work for the rear master was having 600 grit wet and dry wrapped round a felt tip pen, followed by 900 grit, and 1200 grit to finish.  I took my time and made sure I covered all internal surfaces evenly.  Looked very clean when I finished.  There is a tiny hole, I think return hole, which was blocked.  I tried to get it with my smallest carb jet cleaner tool but even that was too thick.  I flooded it with brake cleaner and after a little fiddling around the puddle above started to drain.  Another few squirts and it was clear.  Gave the whole thing a good clean, and good to go.  The front master kit seals went in the rear master and the rebuild went smoothly.

One tip.  I took the full rear system off the bike to set it up.  I had the caliper raised in the vice, tilted to make sure the bleed nipple was the highest point in the system.  I was maybe being too fussy about the bleeding, but the other reason for doing this is there isn't much room to work when the master is on the bike.  Put it on the bike, one last bleed, and I have a very firm and reassuring rear brake pressure.

I will be keeping an eye on the rear to see if the seals hold up.  I don't see any reason that they won't though.  Very happy.  Still have the problem with the front caliper body and think I will have to bite the bullet and buy a new one.  I wish I knew this last week, I could have ordered from David Silver and saved another postage fee! 

Progress ... it goes, stops, and glows in the dark.  One step closer. 

[01Thomas]

Good Going, Eddie!

[eddiebpool]

I've mocked up the bike to get an idea of how it might look finished.  Tank and cowl obviously just primed at the moment.  I really like the primed look but I'm not going to leave it like that.  It has been 2yrs since the bike was torn down so could hardly remember how it looked.  I have a snagging list as long as my arm which I need to get through but I'm getting there.

The front brake was not firming up at all.  I read some excellent tips and tried a few things.  The one that worked was taking the caliper off and letting it hang down.  This stretches everthing into as vertical a run as possible.  I tapped all the pipes / hoses all the way from bottom up a few times over a number of days to release any trapped air.  I had heard that air can be trapped at the banjo bolts so moved them around while tapping to chase any bubbles out of those too.  It seems to have done the trick, almost.  The lever moves about 1 inch at the end before it bites, but when it does its solid.  I notice that the hoses move a bit under pressure which makes me think they are not the best.  I'm considering investing in some better hoses.

One problem, clutch is binding.  I can't get it to free up.  I've stripped it and rebuild to make sure I hadn't done anything stupid.  It all looks good.  I didn't replace any of the friction discs / plates or springs because the all measured within tolerances.  My bike was stored away for 26yrs so I'm thinking it might be an issue with the friction discs, but they measured well within spec.  Any ideas?

Lots of wee jobs to do so hopefully finished soon.