Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: onethumb on February 18, 2017, 02:03:12 PM

Title: Removing head with engine in.
Post by: onethumb on February 18, 2017, 02:03:12 PM: So just noticed that number one cylinder is blowing air back through the carb. I've slackened of the tappets and although not as bad it's still there. Bad times.
I don't want to take the engine out so what are the thoughts of people on here about doing it with the engine in place.
Is it possible that the seats are original from the days of leaded?
Please help I'm a bit down after how close I was to finishing.
Thanks. Steve.

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Title: Re: Removing head with engine in.
Post by: MarkCR750 on February 18, 2017, 02:20:56 PM: Sorry Steve it's just not possible, be sure you have got a problem with the valves though, do a compression check.
Title: Re: Removing head with engine in.
Post by: onethumb on February 18, 2017, 02:29:00 PM: Thanks mark. Is that not possible about the seats or removing the head with the engine in?

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Title: Re: Removing head with engine in.
Post by: hondarc166 on February 18, 2017, 02:55:25 PM: i think it's removing the head
Title: Re: Removing head with engine in.
Post by: onethumb on February 18, 2017, 02:56:51 PM: That's not god news.

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Title: Re: Removing head with engine in.
Post by: royhall on February 18, 2017, 03:07:58 PM: Sorry head won't come off unless you remove the engine or cut the frame tubes and weld in a removable section.

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Title: Re: Removing head with engine in.
Post by: Bryanj on February 18, 2017, 03:39:31 PM: Valve seats are fine for unleaded, what engine is it as the F2 wears out valve guides
Title: Re: Removing head with engine in.
Post by: onethumb on February 18, 2017, 04:35:29 PM: Hi Bryan. It's the 1978 f2. Doh. Any recommendations for getting new ones pressed in, and do I now do all of them?

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Title: Re: Removing head with engine in.
Post by: Bryanj on February 18, 2017, 06:42:18 PM: You will need to remove and totally strip the head and check for wear between valve stems and guides, if new are required (exhaust wear more than inlet) you need to find a motorcycle competent machinist as the guides need reaming to size after fitting and the valve seats will need re-cutting. I believe there is an American firm that does replacement parts but be prepared to sit down before getting prices, I would expect just the work to be over £100 and parts £200+ not including gaskets

http://www.dynoman.net/engine/valves/index.html#F2 Valves and guides $250 ish plus shipping
Title: Re: Removing head with engine in.
Post by: Trigger on February 18, 2017, 07:07:01 PM: Quote from: Bryanj on February 18, 2017, 06:42:18 PM
You will need to remove and totally strip the head and check for wear between valve stems and guides, if new are required (exhaust wear more than inlet) you need to find a motorcycle competent machinist as the guides need reaming to size after fitting and the valve seats will need re-cutting. I believe there is an American firm that does replacement parts but be prepared to sit down before getting prices, I would expect just the work to be over £100 and parts £200+ not including gaskets

http://www.dynoman.net/engine/valves/index.html#F2 Valves and guides $250 ish plus shipping

Valve seats re- ground Bryan ;) Old Honda seats do not like to be cut ;D
Title: Re: Removing head with engine in.
Post by: royhall on February 18, 2017, 07:09:43 PM: Would that be because you now have a valve seat grinder Trig?
Title: Re: Removing head with engine in.
Post by: Trigger on February 18, 2017, 07:11:09 PM: Quote from: royhall on February 18, 2017, 07:09:43 PM
Would that be because you now have a valve seat grinder Trig?

Yes I have a Honda one ;) >>> http://www.sohc.co.uk/index.php/topic,11733.0.html
Title: Re: Removing head with engine in.
Post by: onethumb on February 18, 2017, 07:32:36 PM: Trig, pm sent.

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Title: Re: Removing head with engine in.
Post by: Bryanj on February 19, 2017, 01:16:50 AM: You are quite right but most people associate "ground" with a stick and paste not what we understand mate
Title: Re: Removing head with engine in.
Post by: Trigger on February 19, 2017, 06:30:53 AM: Lap ;D
Title: Re: Removing head with engine in.
Post by: onethumb on February 19, 2017, 09:48:03 AM: Bryan and trigger I'm one of those people

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Title: Re: Removing head with engine in.
Post by: Bryanj on February 19, 2017, 10:56:06 AM: You are right Trigger, but on the tin it sez Grinding paste usually coarse at one end and fine at the other
Title: Re: Removing head with engine in.
Post by: Trigger on February 19, 2017, 09:49:04 PM: Quote from: Bryanj on February 19, 2017, 10:56:06 AM
You are right Trigger, but on the tin it sez Grinding paste usually coarse at one end and fine at the other

Mine definitely says Lapping paste ;) Should I be using Grinding paste Bryan ?
Title: Re: Removing head with engine in.
Post by: archmill on February 19, 2017, 10:59:40 PM: Bought valves, valve retainer plates, guides and stem seals from cyclex in USA for £260. Adding postage, VAT and auntie Teressa's cut ( import duty ) came to £350. The valve retainer plates are to stop the valve collets pulling through, which is exactly what happened before I got the bike
Title: Re: Removing head with engine in.
Post by: archmill on February 19, 2017, 11:02:34 PM: P.S. you can't remove the head with the engine in place. I made and fitted a frame kit which allows you to remove a section of frame, them you can remove the head and cylinders.
Title: Re: Removing head with engine in.
Post by: Bryanj on February 20, 2017, 06:16:21 AM: Thats cos you got new stuff Trig, mines from the 70's still
Title: Re: Removing head with engine in.
Post by: onethumb on February 20, 2017, 03:16:19 PM: Trigger thanks for the info. I spoke to Barry this morning,(he knows his onions!) I'll be getting it to him as soon as I've stripped the whole bike down again and removed the head.
Thanks again.
Steve.

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Title: Re: Removing head with engine in.
Post by: Trigger on February 20, 2017, 07:14:24 PM: Quote from: onethumb on February 20, 2017, 03:16:19 PM
Trigger thanks for the info. I spoke to Barry this morning,(he knows his onions!) I'll be getting it to him as soon as I've stripped the whole bike down again and removed the head.
Thanks again.
Steve.

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Sorry I could not sort you out but, only if you wanted to join the waiting list.
Have you done a compression test yet ?
Title: Re: Removing head with engine in.
Post by: onethumb on February 20, 2017, 08:39:39 PM: Hey no worries thanks for the info and the contact.
Not done the test yet I'm away from the bike this week so I'll test it next week on the kick start then I'll remove it from the frame ready to strip.
Anything I should look for that might show up something other than a head issue?

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