Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Coppertop1234 on August 31, 2015, 09:53:53 AM
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Project 2 (1978 F1) has issues with the head so we are looking for a replacement top end.
I have seen an F2 head on eBay in UK and think it would be a straight exchange?
Any advice please
Cheers
Keith Snr
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Project 2 is an F1? An F2 head can be made to fit, but it's a lot of hassle to keep it oiltight due to mods to the lubrication and oilways/return passages in the head, and are notorious for rapid valve/guide failiure, and very expensive to source replacement. Far better to look for the correct head, also shared with the 750K7. I understand that earlier K heads will also fit, but you'll need to get advice from Bryan or Trigger as to what's involved
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I may be wrong but if I remember correctly the F2 has domed pistons and larger volume hemispheres in the cylinder head so you will be lowering the compression, here's some info from the US site, http://forums.sohc4.net/index.php/topic,99165.msg1105940.html
There is probably more information over there.
Cheers
Dennis
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Most definitely not the same. The F2 head is unique to the F2, bigger valves being the biggest difference. Don't think it would fit either, dowels are possibly different.
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+1 with Roy on the F2 head, will be a nightmare to get it right. Some of the F1's had domed pistons, but even that head is not a straight swap.
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So the F2 head is out of the running - Thanks for info
Will the K6/7 series be a possible replacement.
Seen some in USA, but expensive when postage and customs have had there bite of the cherry
I am struggling to find a 1976 F1 in decent condition, has anyone got one they would wish to part with?
Cheers
Keith Snr
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Not sure K7 is different. I had one but I gave it way yonks ago to someone on here.
Think the K6 would be OK though
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K7 will fit, the K7 used the F1 engine, but fitted with those awful carbs similar to the F2
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Reference the comment valve guide failure on f2s. As a point of interest, I have just ordered new cast iron APE f2 valve guides in the UK for under £70 the set. In stock.
Found a supplier...Suzuki performance spares. They have a website and are Honda also.
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I can see the bronze guides there, but not the cast iron ones, do you have a link?
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i think the guys name is Nick. They may not be listed but he has them,
I confirmed there f2, he seems quite knowledgable .
The bigger f2 valves I have ordered from him are coming from the USA and are kibblewhite and will be about 2-3 weeks although double the cost of other valves.
Springs are also in stock.
I will most likely order the big bore kit from him at £ 495 as it's also in stock
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Got my F2 Kibblewhite valves from CycleX in the States. Good price and fast delivery. I'm told the original guides are a good replacement as they were changed later on for harder items that wear less. As they kept the same part number, I believe it's called a delta change part?
Sent from my GT-I9305 using Tapatalk
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Found this one in USA seems to be correct 1 for a 1977 CB750 F1 ?
http://www.ebay.co.uk/itm/77-HONDA-CB750-SOHC-CB-750-K-HM272B-ENGINE-CYLINDER-HEAD-/231635611814?hash=item35ee8ef0a6
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Ouch on the postage,vand don't forget george osborne will want his cut (whatever import duty it attracts, plus 20% v.a.t. on the purchase price, postage and import duty!) plus royal snail adding at least £12.00 for acting as tax collectors!
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Found 1 in Uk but its from a 73 so early K series unsure if it would be compatible or http://www.ebay.co.uk/itm/321466019903?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Better price but will it fit a 77 F1?
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Hi Keith I have a cylinder head I would be willing to sell and I'm sure its off a F1, i'll get some photos of it today and send them to you ;) cheers Mick.
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Cheers Mick
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Hope this helps. Here is some pictures of a CB750F1 head.
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Thanks to Mick I will soon have a replacement head for our project.
Many thanks for your comments and assistance.
Cash is to hard earned to be spending on the wrong items
Cheers
Keith Snr
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Hi coppertop do you live in Rotherham .I no a guy who lives in mexbrough and he has a garage full of parts for f1 & f2 been over there to day got a exhaust valve off him .he has several heads too .if you need anything pm me and I will give you is number .Cheers yozzer
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Project 2 the Yellow 1 is now up and running fine with the new head provided by Mick.
The head was spot on a little work on valves and it fired up first time with no top end knocking .
The old head was a K7 head and the cam tower threads were all stripped letting the cam rattle about - not good. so with a little help from Mick it was easier to do a straight swap over. Still plenty to do but she's up and running on the road.
Cheers
keith Snr
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Nice one Keith glad to see another old bike on the road 8) cheers Mick.