Author Topic: Smokey rebuilt 350  (Read 7837 times)

Offline hairygit

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Re: Smokey rebuilt 350
« Reply #15 on: May 17, 2017, 08:22:05 AM »
Was your gasket set a genuine one Roy? I'm not certain but maybe Honda modified it part way through production ( like they did with the 750's) and CMS may have the later parts diagram on their website, and any pattern gasket set would contain enough seals for the later models.

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Offline royhall

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Re: Smokey rebuilt 350
« Reply #16 on: May 17, 2017, 06:01:48 PM »
The gasket set was a Cruzinimage item and to be honest not the best. Doubt the spec would have changed as it was only a two year model. Mine was an early 1972 bike and it had all eight seals fitted. To be honest the engine did not look like it had been apart before either.
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline royhall

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Re: Smokey rebuilt 350
« Reply #17 on: March 14, 2018, 03:27:48 PM »
Sorry this has taken so long to resume, been busy building a Suzuki GS1000....... The story so far, my rebuilt CB350F has done 272 miles and pot 4 was smoking so badly I had to take it off the road.

Now the GS1000 is out of the way I decided to strip the top end to have a look, and I'm glad I did.......I stipped it down to the crankcases to look at the pistons. When the head came off all four piston crowns were covered in oil. On checking the gaskets and mating surfaces there was clear evidence of head gasket failure. There was hard burnt on oil deposits behind the head gasket metal sealing ring on all four pots and the gasket was very oily.

I had initially suspected that when the rebore was done it had been bored to a loose tolerance. On measuring the bores and piston skirts the clearance is 0.0008" which is bang on the money for Cruzinimage pistons. Checked the top rings in the bores and the ring gaps are between 6 &8 thou which is also spot on. The new bores appear to have run-in well with a slight glaze but the honing still visible. Strangely each bore has some light vertical scoring that appears to be from the ring ends as they are spaced about 120 degrees apart. Is this scoring normal, its not deep and can barely be felt with a finger nail. I have a new set of plus 1mm Cruzinimage pistons on the shelf, that due to a wrong delivery I got for free, and am toying with the idea of having it bored again just to be sure.

On the head, I tested for valve leakage with the old fill with petrol trick and all is good. That said though, whilst the head is off I am going to replace all eight valve stem seals again just to be sure, and also re-check the valve guides for wear whilst they are out. I solved the mystery of the exhaust stem seals, they had all eight fitted for the first 9 months (approx) of production then further models had the exhaust seals removed. Mine is a very early 1972 model hence the 8 seals. I have checked both barrel top and head for flatness (they were both skimmed at rebuild) and they are spot on.

The questions are how far do I go putting it back together, and clearly I won't be using any more Cruzinimage gasket kits. I have an Athena set for the rebuild (not sure how good the quality of those are) but now I have found that the head gasket was the culprit, should I search for a genuine NOS Honda head gasket? Also what about the rubber seals around the dowels, are they up to the job. I am assuming they are the same items on the 400/4. And how much should the honing be glazed, and what about the vertical scoring is that the cheap Cruzinimage pistons or is it normal.

There are quite a few documented head gasket failures on the USA site but these are mainly leaks to the outside from the edge of the head gasket around the oil control jets. Mine appears to be similar but leaking into the cylinders instead. I had no show of oil at all on the outside of the engine.

Sorry about the long post and the endless questions, just don't want to have to go down this route again. Cheers all.
« Last Edit: March 14, 2018, 04:53:30 PM by royhall »
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline Bryanj

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Re: Smokey rebuilt 350
« Reply #18 on: March 14, 2018, 04:53:36 PM »
There is a post on the US site where he has had a lot of trouble with burning oil on an overbored 350 and has not yey cured it

Offline royhall

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Re: Smokey rebuilt 350
« Reply #19 on: March 14, 2018, 05:01:29 PM »
Have you got a link to it Bryan. Cheers.
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline kevski

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Re: Smokey rebuilt 350
« Reply #20 on: March 14, 2018, 08:52:02 PM »

Offline royhall

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Re: Smokey rebuilt 350
« Reply #21 on: March 14, 2018, 08:58:44 PM »
Not sure it is Kev, I saw that thread earlier this week but it's 5 years old. Sounds like Bryan is talking about an ongoing thread.
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline Seabeowner

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Re: Smokey rebuilt 350
« Reply #22 on: March 14, 2018, 09:38:05 PM »
It would be this on. I think he has given up at the moment and will pick up later.

http://forums.sohc4.net/index.php/topic,165714.0.html

Cheers
Phil
1971  CB500K0  Candy Jade Green or Candy Gold
1973  CB500K1  Candy Ruby Red
1975  CB550F1   Shiny Orange
1978  CB550K     Excel Black

Offline royhall

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Re: Smokey rebuilt 350
« Reply #23 on: March 15, 2018, 06:55:03 AM »
It would be this on. I think he has given up at the moment and will pick up later.

http://forums.sohc4.net/index.php/topic,165714.0.html

Cheers
That looks like the thread, will take a while to read right through it though. Thanks for that.
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline MrDavo

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Re: Smokey rebuilt 350
« Reply #24 on: March 15, 2018, 07:24:46 AM »
Sorry to read of your woes, CMS have the genuine Honda head gaskets, certainly with my CB750 it cost nearly as much, delivered from Holland plus VAT, as two Athena full sets, but there was a big difference in quality  :-\ 

The Athena head gasket from the set I bought is still on the garage shelf. It’s free if anyone wants it, but I wouldn’t bother.
1969 Honda CL450 'Scrambler'
1974 Kawasaki Z1A
2005 Harley XL1200R Sportster
1985 Porsche 911 3.2 Carrera Sport
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Offline kevski

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Re: Smokey rebuilt 350
« Reply #25 on: March 15, 2018, 08:24:22 AM »
Well from what i have read up on this particular subject the main problem seems poor quality gasket sets in particular the two rubber rings at either end of the head, does this same problem occur with the 400, if i eventually have to do mine i can see modifications coming on.

Offline Nurse Julie

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Re: Smokey rebuilt 350
« Reply #26 on: March 15, 2018, 01:23:51 PM »
I fitted extra 'O' rings around the end studs on my 400 rebuild, as suggested by Trig.
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Online K2-K6

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Re: Smokey rebuilt 350
« Reply #27 on: March 15, 2018, 08:04:24 PM »
I've read through that thread on net site,  and something they are missing which may have a parallel here is those ring markings vertically in the bores.

That says to me that the piston rings are not round when compressed into the bore,  else the ring's ends would not protrude further than their outside diameter (and make the marks you can see) that is not right. His question about black ring coating, and should it wear, shows that the rings are not touching the bores where the coating remains. They are, in effect, elliptical in shape. That will not seal the bores either oil going up,  or compression going down. It should be getting to something like 175 psi,  it's nowhere near.

Leakdown testing is only going to show efficiency in holding compression,  it'll not show oil retention ability as that's the opposite direction.

Exhaust valve guide leaking doesn't usually affect combustion chamber as it's introduced after the cylinder. It'll smoke yes, but just from passing oil into a hot exhaust system.
Inlet guides leaking usually show with throttle shut on overrun,  inlet vac goes high and pulls in oil,  when you get back on the throttle it'll puff out a single-ish cloud of blue smoke.

Looks like the rings aren't working as they should,  whether they'll bed in if they're not touching in the first place I doubt it. You'd, in effect, have to wear all of the "touching" parts of the ring down first before that process could even start to take place.
But as the first example of massive ring gap,  that's what you'd get by the time you had achieved the above. There's lots of evidence in that thread but it's not being connected.

Offline royhall

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Re: Smokey rebuilt 350
« Reply #28 on: March 15, 2018, 10:54:05 PM »
I fitted extra 'O' rings around the end studs on my 400 rebuild, as suggested by Trig.
More information if you would Julie. Cheers
Current bikes:
TriBsa CCM 350 Twin
Honda CB350F in Candy Bacchus Olive
Honda CB750F2 in Candy Apple Red
Triumph Trident 660 in Black/White
Triumph T100C
Suzuki GS1000HC
Honda CB450K0 Black Bomber
Honda CB750K5 in Planet Blue Metallic (Current Project)

Offline Nurse Julie

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Re: Smokey rebuilt 350
« Reply #29 on: March 16, 2018, 05:46:41 AM »
If you look back through my engine rebuild thread Roy, there is a pic etc on there. I'm laying on the beach in India so defo not thinking of anything made of rubber in this heat !!! :o
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

 

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