Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Robbo on April 06, 2012, 06:49:33 PM
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I've had two solid weeks in the workshop and my bike has it's MOT tomorrow.
Here's a list of what I've done so far:
Stripped all the PRR fairings and tank for restoration at a later date
New caliper pistons and seals all round
Stripped the front caliper paint
New brake pads all round
New Loom (biggest, longest, most tedious job of all)
New front light (from double to single)
New rear lights
Handmade rear light/number plate bracket
New indicators (including building a separate indicator loom and installing bulbs and holders to the instrument panel)
New clutch plates and bearings
New cables all round
New plugs
Stripped and lacquered 400/4 tank and fitted it to the frame
Made and covered a new seat
New air filters
Carb strip down and repair - replacing all internals, jets and gaskets
New grips
Fixed exhaust - stripped of old baffles and new ones put in (but will probably get a new Marving one)
New side and center stands
New battery, fuses
Made a new horn button - looks great!
New horn
Adapted and fitted an older K series front mudguard
Fitted some john tickle style headlamp fork clamps
Stripped and repaired both master cylinders
Made some racing number ally side panels and vinyl cut stickers and edging ('79 - year of the bike)
Cleaned up all the chrome but left all the black paint on the engine half coming off - adds to the rat look...
I will post some pictures when I work out how, fingers crossed for tomorrow - it smokes a bit from the 4 into 1 when the revs are high and a small leak from the oil filter housing but aside from that all seems good, can't wait to ride it.
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Wow Robin, you have been busy, lookforward to seeing the pictures, good luck with the MOT
Pete
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Sounds an interesting project, looking forward to the pics, good luck with MOT!
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Passed with no advisories! Did a 50 mile coastal ride to celebrate - it was great, bike handled really well but my goggles dug into my eyes at any speed over 80 so I didn't open her right up. When I finally get on the computer I'll load some pics as my phone won't do it!
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Woo hoo! Well done.
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I noticed my trousers were oily on one side today and the block seems quite oily. It looks like its not coming from the head (and I think I the head gasket had gone it would be quite apparent?) but from number 3 downpipe area. I've got new pipes on order anyway so I'll do some investigation when I take the old ones off.
Anyone had any experience of this or any idea what it might be before I investigate further?
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Couldn't see from your list of work done whether you have done any engine work? my guess would be its an oil way leaking, would suggest you check asap and before any more ...er ..... high speed rides, if it is an oil way the cam could become oil starved and ........ well y'know. seriously hope I am wrong as it could mean the head having to come off = engine out, but better safe than sorry. To be fair though cam problems are usually caused by oil way blockage rather than leaking, but leaks must reduce oil pressure if they are bad enough.
Another possibility would be the cam cover gasket ot tappet cover seal, that should be easy to see though. Just how bad is leak?
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If its a 750 it could be the "pucks" that seal the large holes under the cam towers. Before I stripped my engine down it was leaking out of the head fin area between number 2 and 3 pipes. Found these seals had deteriorated due to age.
Rob
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A real common leak problem on these F2's occurrs when the 4 main studs in the middle that hold the head down let oil through, if you look at a parts diagram for F2 you will see these four have a copper washer and a dome nut to stop the oil seeping down the stud, these four studs are open to the elements, they can be seen through the fins hence they are always the rusty ones when you take it apart
Another place common for leaks is as mentioned the cam pucks
A place where oil leaks often get overlooked is the cam tower holding down studs, these are drilled straight though and so if not sealed when reinstalled will let oil in to the spark plug area which will eventually work its way down
Then there is the problem of the head gasket original F2 gaskets have a sealant built in to the gasket, the aftermarket ones have not, i did what K2/K6 does and i sealed my gaskets down with hylomar which can be bought in spray cans
There is also the simple rev counter seal leak the oil will often leak from hear i know cause mine did
Your problem is robin that with all the info in the world it is a rea;l pain in the arse to fix any leak on these cause the engine has to come out even if you want to change the rocker gasket ,
Pete
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I took the tappet covers off and checked for oil - they all seemed to be lubricated ok, I know it's not the best way to check but it's a start. I cleaned it up and ran it for a bit, after about 10 mins a little drip hit the floor and it came from the number 3 downpipe, where it had dripped from the number 3 exhaust pipe joint at the head. The cam cover is all clean as are the spark plug recesses as far as I can tell (I stuck a rag down to check for oil - lots of shit, no oil).
I am changing the exhaust anyway so I will get it up on my mates ramp and have a good look around. Taking the engine out is a last resort as I have a slipped disk currently and no way of getting it out apart from humping it out by hand - that and I am a bit weary of taking it out incase I break something in the doing of it. I know I probably should but....
If it is originating from the exhaust joint, any idea of the causes? I have read all of the above replies and will investigate further. Hopefully it's something I can do in frame otherwise I'll have to bite the bullet (if I do that I may as well go the whole hog - re-seat the valves, polish the ports and all the rest of it which will mean no bike for the summer).
On a side note I checked the plugs, 1 was black, 2+3 were normal, 4 was grey (too lean) pipe 4 is also much hotter than the rest. They are all jetted the same, is this to do with balancing the carbs as I thought I had done a pretty good job by eye and a home made feeler guage. Might be time to get vacuum gauges on the go?
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Was the drip definitely oil, it could be unburnt fuel with oil and soot getting out from the exhaust gasket area due to flooding or incorrect mixture
Pete
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If this is an F2 aren't they known for sometimes higher than normal wear on exhaust valve guides? could this be the cause bearing in mind the mention in an earlier post of a smoky exhaust? If that much oil is getting through it would have thought you might be able to check it by removing exhaust and plugs and wizzing it over on the starter perhaps. Alternatively I would have expected valve guide oil to all be burnt, perhaps refitting the exhaust with new copper gaskets to ensure a good seal would give an idea, if the leak stops but the zorst gets smokier that could be your culprit.
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Pete - it's definately oil, but good idea to cover the bases
Waggles - it was smoking before I did the carbs, I had 125 main jets and bored out pilot jets fitted previously.
I've ordered a new exhaust and will fit new copper seals when I put it on, if it's still leaking or smoking I will have to take the engine out and give it a good going over
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If its oil you are wasting your time changing the exhaust, it will be comming from one of the already mentioned places
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I'm changing the exhaust as mine is full of holes and has no baffle what so ever.
I think I am going to take the engine out of the frame and check the bolts and cam seals - is it worth replacing the exhaust valves whilst the engine is out? Any other worthwhile things to do whilst I have the chance?
Robin
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My exhaust change idea was merely to hint at whether the valve guides were the problem before the motor comes out.
Check guides etc and if in any way suspect replace. I would recommend you get Hondamans book, expensive but that kinda knowledge built up over the years is priceless. There is a lot of stuff in there on improving top end oiling etc.
As for other stuff, depends on the mileage of the motor and how far you are stripping it really.
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Was just idly searching through some old files and came across the attached, no idea where I got it, I just post here for the advice regarding valves. I have no experience of F2s, hopefully someone who has will add their comments on this, just thought it might be useful. In case you can't read it clearly it says:
"Stamped steel retainers are used on all models. On F2 models with their heavier springs retainers often fail. Also keepers seem to 'work' against the valve stems leading to valve failures. In either case severe engine damage can occur. Replace retainers (or complete spring set) and valves when you have any F2 apart"
Comments anyone?