F2 Engines

[UK Pete]

I have just got an 1978 f2 minus engine, and stripped it down, and am in the process of ordering up all the bits needed for rebuild/restoration, up until today i have been really excited about it almost obsessed, i have just dropped off the frame and swing arm off at the powder coaters, and i have managed to track down an engine of the same year, so you would think all was good, well no it is not i have read up and discovered that every body seems to slate the f2 off with its comstars and apparently crap engine i am really peed off to find out the engine in the f2 is no good, before i totally loose interest and shelve the project, possibly sell it on, is there any body hear that has a good thing to say about the f2 especially the engine or is there anything i can do to the engine to make it better as i will be taking it apart and rebuilding it anyway, as you can probably tell i am a bit down hearted now maybee i should have joined the forum before getting this model.
Pete

[dave400]

Sell it and buy a 400/4 
I'm sure you can fix that F2 engine up or use the F1 engine if it's a better choice.

Cheers

Dave

[Spitfire]

The F2 was a big improvement on all the CB750's that went before, it had the most powerfull engine of them all with a beefed up bottom end, new cylinder head and carbs with injectors. The brakes were the best ever fitted to a CB750, the Comstars are a matter of taste, I like them. The frame is the same as the F1 and certainly handles a lot better than the previous CB750's.
So you have good handling, good brakes, a powerfull engine with one weak spot which can be cured by fitting another motor from any SOHC CB750.
The engines  weakness is in the valve guide department, expect problems at 30k miles, it can be fixed but it is expensive.
The great news is that the F1 engine will fit perfectly and if you paint it black only the carbs will give it away.
The F1 engine is solid and restored power levels back up to the early CB750 standards, I don't know what my F2 engine is like as I have never heard it run, but if it is no good I will fit an F1 motor.

Cheers

Den

[mick]

Hi Pete, i wouldn't get to down hearted about the bike, like Den says the problems can be sorted & if you dont want to go that route the F1 motor slots straight in, ive owned loads of bikes over the years & some of them have had some really crap write ups in the mags but ive found the bikes to be ok with no issues, keep going with your resto and you will enjoy the bike for what it is  cheers Mick. 

[Bryanj]

As an ex dealer mechanic of the period the only thing that goes wrong with the F2 engine is the exhaust valve guides, fit new ones and you are OK for about 30,000 (more if you get the later super hard replacements but be advised you WILL NOT be able to fit them yourself!!)

[UK Pete]

Thanks guys for the upbeat replys, i have slept on it and have decided i will keep the bike as i really like the look and it is from that era when i was a teen and dreamed of owning one of these, i am picking up the engine some time this week no doubt it will be worn out, can anyone steer me in the direction of where to get the parts i need to put right the top end , is there any one who does the head work needed, possibly doing an exchange .  or is there any way i can fit the head and cams off a k model if so does any one have the parts for sale,
thanks in advance for any help
Pete

[Spitfire]

The complete top end of a K model will fit the F2 bottom end, pistons, barrels, head, carbs etc. This will give the best of both worlds as the F2 bottom end is beefed up. But it may cost more to do it this way, you might be better off getting a complete K/F1 motor.

Cheers

Den

[Bryanj]

www.davidsilverspares.co.uk
www.cmsnl.com
www.westernhillshonda.net

carfull with the westernhills honda site as it says everthing is available but it isnt.

As to headwork any competent motor engineering (as in re-bore re-grind etc) should be able to do the job but do check that they "understand" motorcycles first.

From base gasket upwards EVERYTHING must be from the one model no mixy matchy but it could be K,F1,F2

[SteveD CB500K0]

You could try www.allbikeengineering.co.uk in Greenwich.

I don't know whether they'd undertake work on an old bike - ask them.

They specialise in suspension and brakes (they did the discs on my Triumph Trophy). Even if they won't/can't do headwork, they are bound to be able to recommend someone in the area.

[Yoshi823]

I loved my 750F2...once i'd modified the frame.

As to the engine...mine responded well to a polished balenced lightened crank and conrods, lightened rotor,reprofiled cam,S&W valve springs,aluminium/bronze valve guides,undercut gearbox,modified oil pump,polished ports,h/d camchain,polished carbs,823cc Yoshi pistons,etc. That engine pulled better than a friends GS1000.And with the uprated suspension and brakes,went around GS1000s as well.
As you are in Sidcup there is a guy in Biggin Hill called Phil Lovett (01959-71592) that I have used in the past for valve seat cutting.Not too sure if he is still there but you could always try him.

I bought CMA cast wheels for my F2 because I was fed up with trying to clean the Comstars.But Big John who used to be the manager at Watling Tyres in Lewisham said that they were some of the best of the wheels that came from Japan,and he would not have said this for no reason.

I have loads of magazines about the F2 and it's siblings (Phil Read Replica etc) so if you need any info PM me as i'm only in Welling.

[UK Pete]

Thanks Yoshi, do you still have your F2?, i am off to pick up a F2 engine today , fingers crossed it might be ok, but i doubt it, one obvious problem is it seems to be missing the oil filter housing i really hope its not in need of too much as i have already exceeded my budget on this bike, and i have only just started ,   you must have spent a fortune on your engine.
Pete

[Yoshi823]

Unfortunatley the bike was written off in a head on with a car on the way home from the Pied Bull down in Farningham back in 1992.

I have a spare 750F2 oil filter housing/oil filter bolt/oil filter as well as a box of other bits and pieces.

PM sent with my details.

I did a lot of the work myself on my F2 so it was time rather than anything else.But then I have a big workshop.

This was on the Mayday Run back in about 1991 and was the last incarnation before it was written off.

[UK Pete]

WOW what a waste of a beautiful bike, i do hope you or whoever was riding it came out of it OK, i will give you a call about the oil filter housing.
Many thanks Pete

[UK Pete]

I am struggling to find oversized pistons for my F2 , the cost of getting the 836 kit off dynoman then sent over to UK  including tax and fees ~+ the cost of sending my cylinder off and getting it rebored. Has left me thinking , so I took a honing tool to my rusty bores, the result is ok they are still within tolerence but one of them has a discoloured patch from the rust, strangely enough it is smooth and not pitted just sort of black in colour, if you were to close your eyes and feel the cylinders you would not be able to tell, which one had rust . and I am tempted to take the chance using the old pistons with new rings in these bores, I would like to hear if anyone has been in a similar position, and what they did
Pete

[Spitfire]

That's just what I did to the F1, the bike had done less than 20K miles and the bores were within spec, so I just put it back together carefully and it goes great.
The F2 bores again have done less than 25K miles and are within spec, but there is what looks like a rust stain on one, (it sat out in the rain for a while with no plugs in). I did fit new standard pistons and new rings years ago and will go with them.

Cheers

Den