Author Topic: 78 CB750F3 R2 Cam & rebuild (Read 4620 times)

Vinhead1957 · « **Reply #25 on:** October 03, 2014, 05:47:04 AM »

That looks painful

Old Scrambler · « **Reply #26 on:** October 03, 2014, 09:02:19 AM »

I installed a 'like-new' K4 cam tower in my F2 head with a very lumpy performance cam.............all stock caps and studs..........no problems after a few hours. When you install anything.........be sure the threads are clean.....inside & out. Be sure to use thread-lock on the exhaust side of the tower-studs............and rotate the cam by hand to be sure its not 'seized' in the races.

garyS-NJ · « **Reply #27 on:** October 03, 2014, 12:30:16 PM »

so the K4 tower had the floating rocker shafts instead of the pinned shafts like the F motor. Just as good? good point on the locktite and I plan to helicoil all the 6mm holes. Just took a look at a spare head I have here and almost all the 6mm holes are helicoiled. I have a pair of used late style towers on their way but no idea how the bearing surfaces are.. Now I'm having a tough time finding the 13011-410-601 rings! (after I cleaned the #$%* out of my 410 pistons). Should I be posting this stuff via a build thread?

Old Scrambler · « **Reply #28 on:** October 03, 2014, 12:46:45 PM »

I think sometime during K2 the pinned shafts began.

Search 'new rings' for a source in Ohio or contact Cycle-X. Also post on the 'For Sale or Wanted' page for any specific parts your looking for.

If your doing a complete top-end............a build thread would be good. There is a lot of unknown info about the 410 motors.

garyS-NJ · « **Reply #29 on:** October 03, 2014, 01:51:51 PM »

will start a build thread later or tomorrow. Ken at Cycle X said I'd have a hard time finding the 410 rings and he was right. Honda says the 392 rings will work but I have to wonder... and metric cycle sells rings to fit the '78750F3 but they also reference the 392P/N. ugh maybe I should buy a piston/ring set from weisco...

Old Scrambler · « **Reply #30 on:** October 03, 2014, 05:01:23 PM »

Now you are ADDING to the knowledge base

I would order one set of 392 rings and check for fitment..............then report back............and hopefully order 3 more sets to finish the build. It is VERY reasonable that the rings are the same. After all.............Honda continues to use the same out-side diameter valve-guides in today's cars & bikes as used in the mid-1960s.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #31 on:** October 03, 2014, 05:57:57 PM »

The 392 rings did NOT come out until the every end of the F1/1976 year and AFAIK should fit the 410 pistons. Cross reference them on motogrid. That is IF you can even get those. Send a piston to Total Seal for fitment otherwise.

garyS-NJ · « **Reply #32 on:** October 03, 2014, 08:52:38 PM »

The 392 top ring is much thinner than a 410 ring. Starting out its already thinner than the service limit (as if rings wear in thickness). I'd like to know the ring groove dimensions for the 392 piston. Honda says the 392 riing will work (but they want to sell them) & metric cycle sells a 392 for factor ring stating it's good for the late F models with 410 pistons but I'm not sold yet.

garyS-NJ · « **Reply #33 on:** October 03, 2014, 08:55:08 PM »

Motogrid shows the 410 rings for the 410 pistons in '78 (changed in late '77Fs).

Jerry Rxman Griffin aka MuthaF'er · « **Reply #34 on:** October 03, 2014, 11:04:56 PM »

Yeah, interesting that the 392 rings goes through 77 but not 78??

AND....

the 77 and 78 PISTONS are the same..... so what does this tell us!!

CB750F A (77) MOTORCYCLE, JPN, VIN# CB750F-2100011 TO CB750F-2111489

CB750F A (78) MOTORCYCLE, JPN, VIN# CB750F-2200001

garyS-NJ · « **Reply #35 on:** October 03, 2014, 11:29:44 PM »

The early 77 pistons are 392 and late 77 &78 pistons are 410 and the look different. Idk about the ring grooves and I'm trying to get that info.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #36 on:** October 04, 2014, 04:21:42 PM »

Yeah 77 & 78 PISTONS are definitely different, No question on that! It's the rings that are the same between late F1/F2/F3.

garyS-NJ · « **Reply #37 on:** October 06, 2014, 02:17:08 PM »

all due respect Jerry but on one or two parts look ups I found the 1978cb750F3 calls for the 13011-410-601 and in one of the posts I saw hondaman cautioning against using aftermarket rings where the late 77/& 78 Supersports with the higher compression (410 piston) called for the 410 rings. I have 410 pistons.

there is some confusion tho on the 13011-392-004 rings where I saw one sohc4 member wrote 1.1mm thickness for the first and second ring but then I saw two sellers ( both selling Hui Yang rings and one was Metric-cycle) with nominal thickness of 1.2mm. 1.2mm is 0.047" and right at the ring groove thickness on my 410 pistons. so long story short, I'm a little concerned if the rings came in at 1.1mm (0.043) seeing as my current old rings measured 0.045/046 and also wonder about getting a nominal thicknes 0.047" ring for my 0.047" groove. I sent an email to Norm at Metric Cycles and also the ebay seller. I'm also looking for the ring groove dimensions for the 392 pistons and Hondaman offered to take a look. thanks in advance and I'll be sure to get my build thread going with findings. incidentally, I reached out to a number of ring manufactures and not finding anything there either. there's got a to be a number of 750F3 owners that faced this same problem so I'll check some other forums and post another title specific thread here on sohc4

Jerry Rxman Griffin aka MuthaF'er · « **Reply #38 on:** October 06, 2014, 08:31:59 PM »

Sure, I understand the concern. I'd like to think the Honda phone call was good? Why not order rings for just 1 piston as a test fit? If it does not work I'm sure someone here will buy them from you.

70CB750 · « **Reply #39 on:** October 07, 2014, 04:25:56 AM »

I used 13011-410-601 rings from Metric Cycles. The only difference to original F3 rings was the oil ring. The wave of the new middle oil ring is vertical while the old ring wave was horizontal.

New rings installed:

garyS-NJ · « **Reply #40 on:** October 07, 2014, 06:55:29 AM »

410 rings on a 410 piston? What motor? & when did you buy those rings?

70CB750 · « **Reply #41 on:** October 07, 2014, 07:03:21 AM »

1978 CB750 SuperSport motor - see my K3F build.

I believe it was from this seller:

http://www.ebay.com/sch/metric-cycle-parts/m.html?item=261616736557&hash=item3ce992992d&pt=Motorcycles_Parts_Accessories&vxp=mtr&rt=nc&_trksid=p2047675.l2562&_vinkw=13011-410-601&_vilcat=177980

Spring 2013:

http://forums.sohc4.net/index.php?topic=115305.50

garyS-NJ · « **Reply #42 on:** October 07, 2014, 07:42:09 AM »

do you recall if the pistons and head were stamped 410? and do you recall the ring manufacturer and packaging/part number? Metric-cycle is selling Hui Yang rings now in a blue package labeled with Honda P/N 13011-392-004 and the ad says they fit the 13011-410-601 (and other P/N's). They give ring dimensions of 1.2, 1.2, 2.5. My 410 piston is 1.2, 1.2, 2.8mm and I'm wondering how many people are running 2.5mm oil rings in their 410 piston 2.8mm grooves and with what success. Or did they sell you a red package of rings from Riken labeled 13011-410-601??? Your ebay link got me to everything from Metric Cycle including their 13011-392-004 HY ring.

70CB750 · « **Reply #43 on:** October 07, 2014, 07:54:16 AM »

The head is 410 for sure, pistons - no clue. I will try to find the box the rings came in, but most likely it is gone. As far as I recall, the box was white with label on it and the label said 13011-410-601, I am certain of that.

garyS-NJ · « **Reply #44 on:** October 07, 2014, 09:12:27 AM »

thanks prokop. now I'm thinking I know why I picked up the F3 bike and then later a spare parts motor for so cheap. I might try to Frankenstein the oil rings if I can't get something soon. or use my old oil ring cuz I figure it's the top two rings that matter most..

70CB750 · « **Reply #45 on:** October 07, 2014, 09:42:50 AM »

Yeah, I learned the same lesson

IMHO you could cut your losses and go with early K engine.

My F3 had only one broken ring - the second from top - if the rest can be of any use to you, you can have it for the postage.

garyS-NJ · « **Reply #46 on:** October 07, 2014, 11:26:45 AM »

haha, thanks Prokop. I'll cut my losses next time around. I got a sweet set of cam towers with nice rockers and caps last night and started to helicoil the 6mm cam head threads (my basket 410 head had a bunch done). and metric cycle got back to me today saying their HY 392-004 ringset has 2.8mm oil rings. So looks like I'm golden for this rebuild (cept for maybe valves because I have one bent one and most of the stems are a little gauled.)

Old Scrambler · « **Reply #47 on:** October 07, 2014, 11:41:47 AM »

Lots or research time..................I appreciate it

I have a few valves..............some are better than others............Need to keep one complete set for myself.

Let me know your needs...........intake, exhaust, how many of each.

Postage only........... for your work

garyS-NJ · « **Reply #48 on:** October 07, 2014, 12:38:21 PM »

Wow thanks. Will do.

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Author Topic: 78 CB750F3 R2 Cam & rebuild (Read 4620 times)