1972 Honda CB175 Super Sport restoration

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Cortina
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Re: 1972 Honda CB175 Super Sport restoration

Post by Cortina »

Nine One One wrote:Condenser??????????/
PS Correct answer is NOT : It's a new one therefore must be ok ! .................... OK !
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Yep, new and expensive, so must be good!
Have strong sparks too, but notice micro sparks across the points when running..
Some have suggested too much battery volt loss to sustain the electrics.
Battery now fully charged for another few exciting hours tomorrow.
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Engine back out of the frame this afternoon.
I have engine oil coming out of the one exhaust, wet with oil down the ex port, suspect oil coming down the valve stem.
Will have the head off tomorrow for strip down. :cry:

Anyway, it will keep me busy.
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Confused as ever, but if anyone is reading:

Head off, and removed the LHS ex valve, all seals correct and look good. Port saturated in oil. That must mean the valve seals are not working, but they were new when i rebuilt it and feel good on the valve stem.
Lapped the valve in again with fine and have a text-book light grey finish on the seat and valve rim. All back together.
Did the same with the seal-less inlet, again all clean and looks good, so fine paste and back together.
With plug back in, filled the chamber with cellulose thinner and it stayed there, no leaks past valves or plug.

So, where was all the oil getting in from? I can only suspect the rings, so will go though that lot (esp ring gaps) tomorrow when I re-lap the RHS valves.

Both piston tops are different colour, the LHS with oil is far lighter a straw colour than the RHS piston top.

Thinking of a re-bore.
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coomo
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Re: 1972 Honda CB175 Super Sport restoration

Post by coomo »

Mmm.Does the tickover/running issue alter at all when engine becomes hot?
911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

No, once off choke I can just get to 1800 which is almost stable.

Before pulling the engine I had tried to get it to run, almost refused to start.
Found one plug (LHS/oily side) was only giving a very very very light fizz of a spark from the ceramic. It did this on the other ignition lead, so consider that plug scrap. It was new after the rebuild.
If one plug cannot ground the engine will not start, so...
Found a correct plug from about 1972 and it fired but ran really bad with belches etc from both sides, rough idle speed anything but stable, so, FED-UP, pulled the engine to find out if I screwed the rebuild up.
I think I have a pair of new oversize pistons in the shed that oddly came with the bike, and if good will have the cylinders bored to suit at a local scooter/bike shop. They re-bored my last Honda 5 years ago.
Did a compression test a few days ago, hot, WOT = 110 and 120 psi.

This running situation has gotten worse as time goes on.
I was very surprised not to find trouble with the valves, but the leak-down test I did after the compression test showed total silence at TDC and 20 psi in the cylinder via the plug.

Perplexing.
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coomo
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Re: 1972 Honda CB175 Super Sport restoration

Post by coomo »

I think you maybe right.Only way is too rebuild.
911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Still mystified, but cleared a few other things:
All valves re-lapped, seals all good on the exhausts and all stem diameters to spec.
Engine already overbored to +0.75mm so reluctant to go the full hog and go 1mm over from stock, so have ordered genuine +0.75 over rings from David Silver and 2 new plugs. £63!

Took all the existing rings off:
Using the cylinder block and the matching sides, all ring gaps are 10 thou to 15 thou so on the large side, the second rings being a tightest at 10 thou. so decided to re-ring.

Have to wait now and hope these parts are in the UK and not in the USA.

For a change, I will be quiet for a while...
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

New Honda NOS +0.75mm rings arrived yesterday, so started to look to re-build the engine.
Popped the rings in to find the gaps were still a bit big, in tolerance but only just.
Having seen that made me think and have stopped doing this rebuild.
Also, there is a corrosion break out, a small patch on one bore right at the top which is quite deep, I did not notice/feel this at the first build, so it has got worse during the short running recently and that means a Change of Plan.

Have ordered a used cylinder block which is on stock piston dia with some water marks (as it is described) from a good bike breaker who has sold me lots of bits, all really good when nice and clean.
They recommend a 'first bore over' to clean it up, that would be 0.5mm.

Plan is to have the bore machined 0.75 over so I will have virgin rings and pistons in a virgin cylinder block at the lowest cost.

I think this is the best tac in the long run. That corrosion spot/area (about 6mm dis) is right at the spot the top 2 rings rest at TDC/fire and will just get worse.
It is now also on my mind, and will be a worry if ignored.

Hope to get it all back by Xmas, but that may be difficult. The machine shop I intend to use will be busy.
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Well, of course that did not work.
The replacement cylinder barrel arrived today, cleaned it all only to find a 20mm crack in the exposed part of the one cylinder, and you can see where the piston had been scraping past it at 9000 rpm...

So, pointless reboring it as the crack will never be flat and probably keep progressing.

The supplier I think will credit me back, but only has a barrel set off a cb 175 K0, 1968, and that part number is different to the one I have off the original bike.
Honda would only give it another part number if there is a difference between the two.

Anyone have a skip for this thing? :evil:
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Right, having recovered from this disappointment, got to find a solution!

I have two options and need some info please.
1
I've been offered a barrel set from a cb175 K0, 1968. The Honda part number for this is different to the barrel for my K6/1972.
For Honda to give it a different number, there must be..a difference. The K0 part needs a full rebore to remove rust, and I'm dubious if a 0.75mm over will clean them.
Therefore, this is a high risk action.
Does anyone know if the '68 part will fit the 69 on cb engine? I think the 68 CB is the Sloper??

2
I get (I hope) a credit for the part I've just got, about £60.
I buy a set of 1mm over pistons and rings for £44 from Japan and re-bore my cylinder block to 1mm over from 0.75mm over, I sell by new 0.75 over pistons with real Honda rings for ebay for about £30 (guess).

I'm in for the £60 rebore cost with either approach.

Option 2 seems the best route, buy new pistons and rings, rebore the cylinder barrels I have to suit in the New Year.


Any thoughts on option 1? If I go Option 1 I can use my new 0.75 over pistons and rings.
73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Progress over the last 12 hours.

An internet friend is sending me a spare barrel, stock size to replace my cracked barrel, so today, the duff one was removed.
With the 'new' one in place, I can re-bore to +0.75 to match my new pistons and rings and the engine should then be perfect internally.

Going to miss my Xmas dead-line...

I warmed the block of my scrap original cylinder barrels and without much heat or effort it tapped out with light blows from the plastic hammer.

Encouraged by this, put more heat into the replacement head and the cracked barrel almost fell out!
Thus, I'm ready for the Father 'Richard' Christmas pressie of the barrel to replace it. (the guy who is sending me the barrel for the donation to the RSPCA)

Fabulous!

If this all goes Due South then I have a Plan C, and that will be to have bored the other barrel set I have that is currently a smooth but worn +0.75 over that could take a bore to a full 1mm over and those bargain new pistons and rings from Japan. This 3rd barrel block has 30 thou ring gaps using new +0.75 rings...

All money, but I do want a perfect interior to this troublesome engine.

When I did my Gold CB (1976) it got the lot, bore, pistons, rings, valves everything as the stock parts were knackered. I should have done this lot again.

My new Chinese starter clutch assembly has also arrived a week early, going to fit it now as I can't do anymore on the bike in prep for the re-bore.

That crack was propagating badly!

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73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

The roller-coaster ride continues.
That clutch above does not fit though the supplier in China is insistent it is correct..so that is that.

The 'new' barrel might arrive today which will be good. Have trial fitted another barrel back in using a good heat soak with the heat gun and it just drops back in place, so that is re-assuring.

Looking to the head, this engine design has no oil seals on the inlet valve stems. The exhaust is sealed, not the inlet.
The model after uses car type seals on both sides, so using my spare head I have 2 spare exhaust guides that are a direct fit to replace the plain inlet guides. I have ordered new seals same as the exhaust and so will have seals everywhere.

As the design is, oil has a totally free passage to the top of the inlet guide to run into the running engine which causes smoke and very poor combustion, a problem that has plagued me on this bike.

Run out of time now to get the cylinder bored, and the seals are coming from Belgium so will never be here before Xmas, so balsa wood awaits me! :)
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

CB200 seals arrived today from Wemoto so got going on the head conversion, but not for long...

Knocked the original inlet guides out after some heating of the head casting, easy. Knocked the spare exhaust guides in straight after some more heat and they drifted in well. I turned a drift that was stepped to slide into the guide and a shoulder to rest on the end to save any damage to the diameter.

Did this after measuring the overall length of the really snug fitting seal so to be sure it would not be crushed by the spring top cover/collet cap during use. All good.
The seals are really nice, however...

They are also too big to pass into the inner valve spring by about 0.25mm dia! Really should have checked that, but, being VERY impatient (my wife agrees) I skipped that bit.

However, still moving forward, I also ordered from CMSL new cb 175 exhaust seals which will pop on a dream, and they will be here Wednesday next.

To get the outside valve spring to sit at the right height I needed 2 washers which I turned from oversize steel washers for the spring to sit on levelling everything up using my fab 1944 ex war department Drummond lathe.
Thus play came to an end until Wednesday.

I hope Richard's cylinder turns up Monday so I might 'just' get it machined before Xmas, but that will be a tall order.

Exhaust guide has the shoulder on it, and that is the CB 200 seal.

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73T 911 Coupe, road/hillclimber 3.2L
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911hillclimber
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Re: 1972 Honda CB175 Super Sport restoration

Post by 911hillclimber »

Barrel arrived and heated into the cylinder block a treat.
"No Chance of a pre Xmas re-bore" is the universal message from local m/c shops, so stuck until next year for a full re-build.

Bit of a tease is the piston-to-cylinder clearance to request.

Looks like 2 thou is about right. Would welcome any comments! (piston dia is 52.75mm)
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
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