Author Topic: Need help identifying pistons (Read 4240 times)

smacd11 · « **on:** October 22, 2017, 10:12:31 PM »

I have a full set of forged 836 pistons and a near complete set (3/4) of cast 836 pistons. I think the forged ones are RC engineering Venolia from pics I have seen, the cast pistons appear to be Honda pistons as they have ART cast into them. They both measure 65mm. Any help on these would be greatly appreciated. I would like to know the recommended clearance for those forged pistons.

smacd11 · « **Reply #1 on:** October 22, 2017, 10:13:45 PM »

Here's more pics of the cast piston

smacd11 · « **Reply #2 on:** October 22, 2017, 10:18:33 PM »

And the forged...

Bill/BentON Racing · « **Reply #3 on:** October 23, 2017, 03:26:48 AM »

Those forged piston's called for large clearances.....005 in.etc.You could probably run .003, .0035, the cast one's @ .002

Medyo Bastos · « **Reply #4 on:** October 23, 2017, 04:06:40 AM »

art made pistons for others too including actionfours

smacd11 · « **Reply #5 on:** October 23, 2017, 07:57:23 AM »

Thanks for the tip, I downloaded action fours 1979 catalog from satanicmechanic, pistons look exactly like the ones in the catalog. Anyone have 1 spare piston kicking around so I can complete this set?

Big Jay · « **Reply #6 on:** October 23, 2017, 01:39:48 PM »

The forged piston is an MTC. The cast may be one of ours.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #7 on:** October 23, 2017, 02:10:22 PM »

Jay, stock 350 +1mm or cut down crown?

smacd11 · « **Reply #8 on:** October 23, 2017, 02:25:23 PM »

Forged are definitely MTC - just noticed under the pin it says MTC ALCOA. Are rings still available for these anywhere?

Big Jay · « **Reply #9 on:** October 23, 2017, 03:06:02 PM »

smacd11 · « **Reply #10 on:** October 23, 2017, 03:21:06 PM »

Do you know a part number/supplier?

Thanks for your help.

FuZZie · « **Reply #11 on:** October 23, 2017, 04:59:17 PM »

I can't take the suspense any more!
http://www.aperaceparts.com/

smacd11 · « **Reply #12 on:** October 23, 2017, 05:11:35 PM »

The only rings I see are for the wiseco and je pistons, neither of which will fit the MTC pistons. Wiseco oil rings for but the comp rings don't. I already have a set of those.

Bill/BentON Racing · « **Reply #13 on:** October 23, 2017, 05:38:11 PM »

Try these guys

smacd11 · « **Reply #14 on:** October 23, 2017, 05:42:32 PM »

Already sent them an email, nothing available. Must have discontinued them. From my investigating I may have to buy 2 sets to make them work, BPR650 (I think that's the number I found) should have comp rings that will fit. Just hoping to find a source for 1 set.

cbr954 · « **Reply #15 on:** October 23, 2017, 06:51:25 PM »

Get a hold of MTC, they found rings for my mtc 72mm pistons, they will know the ring dimensions and be able to send you in the direction of who can make them.

smacd11 · « **Reply #16 on:** October 23, 2017, 07:12:42 PM »

Will do, thanks.

PeWe · « **Reply #17 on:** October 23, 2017, 09:48:23 PM »

Not same rings as CB350 + 1mm?
I have 3 sets of 836, all have same ring sizes.
Forged RC 836 with teflon buttons, older cast RC and Action Fours cast marked Art. I reused the 3 piece oil rings from my forged RC on my 30 years later on eBay purchased RC cast with 1 piece oil rings.

smacd11 · « **Reply #18 on:** October 23, 2017, 10:33:48 PM »

Looks like CB350 rings would work but are as hard to get as the ones for these pistons. The ones I located are from Bore-Tech PR650.

PeWe · « **Reply #19 on:** October 24, 2017, 01:17:10 PM »

I looked for CB350 +1 65 mm rings for a while and found these
http://www.ebay.co.uk/itm/Honda-CB750-Piston-Rings-x4-sets-836cc-65mm-1969-1976-Oversize-rings-Big-Bore-/362023996060?hash=item544a4fca9c
Really low price and correct sizes for my pistons. Better than none.

Cruzinimage sells low cost piston sets that people use. I'll install 61mm pistons from them within a few days. All pistons were very similar in diameter and weight + all rings had correct en gaps, no need of filing ends. So cheap might work

Big Jay · « **Reply #20 on:** October 24, 2017, 01:46:28 PM »

See if the ring groove width is the same for both pistons. If so, CB350 twin S4 rings.

smacd11 · « **Reply #21 on:** January 13, 2018, 07:49:01 PM »

Now that it's a new year I thought I would revive this thread. Just curious if anyone out there has 1 Action Fours 836cc piston kicking around - in the boxes of parts I acquired form the previous owner I can only find 3, and he has no idea what happened to the 4th and it would be nice to have a complete set.

The next question would be which would be the preferred piston, the MTC forged or the AF cast? The cylinders I got with the MTC pistons have approx. .006- .007" clearance and the guy I got them from said he removed them because it smoked too much (I'm not surprised!). I found one set of cylinders in my stash that are already bored that would give a final clearance of 0.002-0.003" with the MTC pistons. I'm kind of leaning that way since I wont have to have another set of stock cylinders bored out. From your guys' experience would that be adequate clearance for those forged pistons? I know it would be too much for the cast ones. MTC engineering got back to me saying the clearance for these pistons should be 0.001-0.002". I won't be racing this bike - just trying to put together a fun bike to ride on the street with a bunch of parts I have gathered up.

Cheers,
Shawn

gschuld · « **Reply #22 on:** January 13, 2018, 08:05:34 PM »

This should help.

. Ken Tipton seemed to prefer tighter tolerances than most for the forged piston sellers of the day. Their pistons were also on the heavier side compared to some of the others at the time.

George

smacd11 · « **Reply #23 on:** January 13, 2018, 08:16:31 PM »

Thanks for the info - that helps a lot. I will have to do some more accurate measuring before I commit to this build.

cbr954 · « **Reply #24 on:** January 13, 2018, 08:31:26 PM »

MTC told me to go with .001" with my 72mm pistons from them and Jay told me I could go to .0015 no problem.

PeWe · « **Reply #25 on:** January 15, 2018, 09:35:30 AM »

Dynoman recommend 0.0025” (0.0635mm) for their 1000cc pistons, forged JE 71.25mm.
My old 836 did not smoke with cast pistons and 0.2mm clearance.
That cylinder need CycleX 65.5 mm pistons (849cc).

754 · « **Reply #26 on:** January 15, 2018, 12:00:48 PM »

Man I can't afford to stick a new set of pistons, but then I won't go dragracing the week I put them in..
But.. someone always has so they plan for it.

754 · « **Reply #27 on:** January 21, 2018, 08:10:52 PM »

I got some pistons out if a 78 F model.
These pistons have a high crown, about 5 mm higher than edge of piston .they are marked 410.
The rods are marked s59 and S50.
I thought 77/78 had flat tops due to smaller chamber size.. what do I have here ?

smacd11 · « **Reply #28 on:** January 21, 2018, 08:26:56 PM »

Looks like 77-78 750F used 410 pistons. Found this on ebay:

https://www.ebay.ca/itm/Honda-CB750F-Piston-2nd-OS-50mm-1977-78-13103-410-003-NOS-OEM-NEW/152446644431?hash=item237e8730cf:g:5v4AAOSwr~lYrkDP&vxp=mtr

cbr954 · « **Reply #29 on:** January 22, 2018, 06:55:46 AM »

They are F pistons. The F had larger combustion chamber then the K's. The few I have measured have been 5 to 6 cc larger then the K

smacd11 · « **Reply #30 on:** January 22, 2018, 07:21:57 AM »

I found a post somewhere that said the 77-8 F's (410) had 28cc combustion chamber, the K0-6 (300) were 22cc, and the K7-8/F1 (392) were 24cc.

cbr954 · « **Reply #31 on:** January 22, 2018, 09:31:45 AM »

Thats about what I found for volumes but they do vary quite a bit from the factory.

754 · « **Reply #32 on:** January 23, 2018, 11:29:29 AM »

Son of you used the F pistons in an earlier K, you should get a nice boost in compression, I suspect rings may be pricey.

Medyo Bastos · « **Reply #33 on:** January 23, 2018, 12:01:05 PM »

I use to run ‘em in k’s back in my youth

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Author Topic: Need help identifying pistons (Read 4240 times)