Honda-SOHC
SOHC.co.uk Forums => Other Bikes => Topic started by: neildavies67 on August 24, 2017, 11:09:36 PM
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Hi folks, recently acquired a (non running)1969 CL350 and finally got around to tearing down the top end. Pistons, head and valves heavily crusted in thick carbon deposits and strange pitting on piston crowns. Barrels seem in reasonable shape (although no "crosshatching" visible but was going to re-bore anyway) and compression seemed ok (by feel, not measured). Pistons were measured and are standard but the cam lobes seem like they have been reground asymmetricaly for faster valve closure (I think) - see pics. I assume this was intentional and not due to wear as all the cam lobes appear to be the same shape with some pitting at the apex. If this was a performance mod it seems odd due to standard pistons. Maybe heavy carbonisation due to failure to re-jet after cam mod? I'm just scratching around in the dark here! Anyone seen anything similar before?
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That's a 'fat cam' from a K0/K1/early K2 model that was designated '286' which runs with the associated '286' rockers. The engine was detuned after the K2 and the cam became the '312' part with associated '312' style rockers (312 designation was for the SL350, the first 'K' engine to change over to the detuned cam) . The parts are not interchangeable so need to be replaced in sets if swapping over. I can't do it for a couple of days but I can photo my 10K mile 'fat cam' from my '69 K1 CB350 to compare but seem to remember the profile was similar to yours. Mine is really nice and not worn so will be a good reference. the 286 fat cam is much prized by classic racers and since it was prone to lobe pitting /journal wear if oil changes not adhered too it is a bit of a 'hens teeth' item in decent nick.
Here is a supposed NOS one (286 type)
http://www.ebay.com/itm/HONDA-CB250-CB350-CL250-CL350-CAMSHAFT-NOS-/381992665371?hash=item58f089811b:g:R7wAAOSwtfhYrGS7&vxp=mtr
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Many thanks for clearing that up AshimotoK0. The rockers were heavily worn and I now wonder if the previous owner has used the wrong type? Will check this evening! Do you know if these cams can be hardfaced and re-ground? Can anyone reccomend an engineering firm/cam specialist? Cheers!
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An age old memory tells me that the cams were meonitic cast and the followers hardened. If you harden the cam and followers expect a life measured in minutes not years
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Many thanks for clearing that up AshimotoK0. The rockers were heavily worn and I now wonder if the previous owner has used the wrong type? Will check this evening! Do you know if these cams can be hardfaced and re-ground? Can anyone reccomend an engineering firm/cam specialist? Cheers!
If later rockers are fitted ..real struggle but I have seen it done in the '70's by some idiot... then later rockers (cam followers) are cast with '312' on them. Decent sets of rockers and camshafts do pop up on eBay particularly in the US but occasionally at the likes of DK Motorcycles or GovnorsBridge MC's. IMHO that will be a cheaper and less fraught way than refurbishing parts, unless of course you are building a racer..... The 350K in it's various guises sold by bucket load in the States so decent parts are out there if you look.
Don't worry too much about using the later 312 parts ..it knocks a couple of BHP off the engine but it's still a fair power output for the 325cc designed pre 1968. There are very slight differences between the camboxes for 286 and 312 cams but it's just concerned with shaped apertures slotting the camshaft in and the can be easily modded even with a Dremel tool. Definitely worth joining HondaTwins.net forum as well as this. I have the same 'handle' on there. Having said that you are just as likely to get as much help on here.
The service manual and parts book for your bike are on here in my Dropbox links on this site.
I also have the 69 K0/K1 Parts manual but I have not scanned it yet.
http://www.sohc.co.uk/index.php/topic,8884.0.html
CB350/250K PARTS MANUAL
https://www.dropbox.com/s/2ohbdtqh5nvgvvf/Combined%20Honda_CB350_Parts_Catalog.pdf?dl=0
CB/CL 250/350K SHOP MANUAL
https://www.dropbox.com/s/8i51vjqqdvllazj/CB350ShopManual.pdf?dl=0
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I now think the later 'skinny' cam still had a 286 Part No. not 312 , but the rockers that go with it are indeed designated 312 (see parts book)
https://www.cmsnl.com/honda-cb250k4-england_model8207/arm-valverocker_14431312010/#.WZ_XDPiGPIU
[attachimg=1]
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Thanks for all the info Bryanj/AshimotoK0. I noticed that the rockers on CMS had the number 312 on the casting for early models but wasn't sure if this was just due to a "stock" photo being used? Just had a chat with Newman Cams and they will have a look at my parts. He said they would normally put a stellite pad on the rocker and re-grind the lobes if they weren't too baddly worn/pitted! He di say they have some k4 blanks so am wondering if anything could be done with one of those? Looks like I'm caught between a rocker and a hardface (sorry!).
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In your first post you mention "strange pitting" in the piston crown, this could by associated with detonation in the combustion chamber, ie pinking as it's more commonly called.
In more extreme cases it's sometimes accompanied by scuffing of the piston skirt near to the gudgeon pin boss and can fracture the ring lands of top and second rings.
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Cheers for the info K2-K6! I have posted pics of the pistons below! Going back to the cam and rockers issue, I have also posted pics of the wear on the cam followers and any identifying numbers on the rocker castings. The mystery deepens as there are three different numbers: 11, 26, 8 (or 6) & 11 (although they all seem identical in appearance to me?). The two rockers on the left were located on the left & right inlet cam lobes while the two on the right were located on the left and right exhaust cam lobes. Does anyone know if the numbering is significant? Should I be worried? For the pistons, the badly pitted one was located in the left cylinder. There does appear to be some scuffing on the edge of the piston crown. As i said previously, because the pistons are standard I will be re-boring. Not sure whether to just go up one size or bite the bullet and go big bore kit! Anyone have any experience either way? I will be getting Mikuni VM30s carbs as the Keihins were buggered! I've been quoted £330 jetted for standard.
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Rockers are badly worn all four rockers are same part no. But you must use 312 rockers with later cam and do not use 312 rockers with early cam. Interesting to know how much Newman cams quote you .It used to be Joy engineering back in the day but heard good things about Newman
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I would hazard a guess that the piston markings are ingress of hard crap, are there similar marks on the head? Used to see marks like that when piston rings shattered but that needed a destroyed ring groove as well. Ash is the man to listen to on these motors, but like I said I remember way back in the late 70's a racer friend had a cam hardened and reground and it didn't last a practice along with the hardened followers, Damage on the followers like that is probably bad oil flow as people do not clean out the centrifugal filter often enough
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Evening folks, once again many thanks for the wisdom! This is my first project like this and I'm loving every minute, despite the never ending challenges! This site is an amazing resource and I am most grateful for all the help, the information has been really useful! The head is pretty coked up but no obvious damage although I will give it a clean tomorrow and inspect thoroughly. While the pistons are pretty crappy there is no catastrophic damage with rings and lands intact. Newman cams quoted £60+vat for camshaft re-grind and £37.50+vat for stellite pads on each rocker but this was sight unseen and he asked me to send them in for an initial inspection so price is obviously subject to change. I notice on CMSNL that the rockers for the USA K0 CL350 have no numbers visible on the casting but do have a right angled "hump" on the spine of the cam follower end, the same as my pics, whereas the 312 rockers have a smoother curve on the spine of the cam follower end. Do people think I'm safe making the leap that I have the correct rockers for the early camshaft?
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I am 'darn sarf' at the moment but when I get back I will dig out all of my parts and photo for you. If you have the early cam and followers marked 312 like the CMS pic I posted then they are wrong but if no 312 markings then they will be early 286 parts .Personally I would search for a decent used set ...That's what I did with my CB72 and one of my CB250k0's ...K3 and K4 models used the later camshaft and rockers and will be more readily available than the earlier parts.
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I read that you are considering different carbs. I have considered the same with mine. In a box of bits I have a pair of Amal concentrics with manifolds designed to bolt onto CB350K head. Has anyone tried these and know if it works well or not?
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Got home ...rule #1 stay off the M1 at Bank Holiday time :(
Here are some pics . My late cam is not here so I couldn't photo it.
[attachimg=1][attachimg=2][attachimg=3][attachimg=4][attachimg=5]
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Thanks for taking the time to take those picks AshimotoK0! I think i am now confident that I have the correct rockers, even though mine are badly worn and the numbering on the casts doesn't appear to be consistent. Your cam lobe faces are in much better condition than mine! Do you know if the dimensions for the early asymmetric camshaft are available anywhere? I've had a trawl through google but have come up empty handed! I will call Newman camshafts tomorrow to see if they require them in order to sort the camshaft! Cheers again for all the assistance!
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This attachment may be helpful.
[attachimg=1]
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Interested to see how you get on with Newman cams. If you were opting for the later cam and rockers I would suggest buying good used parts but that early 'fat' cam is rocking horse poo and there are a lot of 'bad' sellers out there that will sell you junk used parts because all of the 350K classic racer guys are searching for them, so they think they have the equivalent of a gold nugget to sell. Even low-milers from the States very often have badly pitted cam lobes because I don't think they changed the oil regularly enough. I got a lovely later cam from DK for not a lot of money but they just put it in a plastic bag and shipped it ..when I received it the auto-advance shaft had broken off due to impact in transit. I got a full refund of course but what a waste of a really rare part.
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Well I've had a chat with Newman Cams and explained the situation. I'm sending my cam off this weekend and they are going to "have a look and see what they can do!". As soon as i get it back I'll post some pics. Unfortunately I will have to send the rockers separately as I've just blown a chunk of my cash on a pair of Mikuni VM30s from Allens Performance Parts which arrived today (only ordered them Tuesday so well impressed with the turnaround)! Hopefully Newman cams will be able to put a stellite pad on the rockers unless I can source some old syle used ones in good condition in the interim. AshimotoK0, do you know if the lift on the fatcam is the same as the later cams?
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Well I've had a chat with Newman Cams and explained the situation. I'm sending my cam off this weekend and they are going to "have a look and see what they can do!". As soon as i get it back I'll post some pics. Unfortunately I will have to send the rockers separately as I've just blown a chunk of my cash on a pair of Mikuni VM30s from Allens Performance Parts which arrived today (only ordered them Tuesday so well impressed with the turnaround)! Hopefully Newman cams will be able to put a stellite pad on the rockers unless I can source some old syle used ones in good condition in the interim. AshimotoK0, do you know if the lift on the fatcam is the same as the later cams?
Sorry been away in Bakewell for weekend but I will compare as I have a really nice K4 camshaft I can measure for you but it's not here at my house, so it will be tomorrow until I can get to it.
Saw a lovely looking 750K2 as we drove through Matlock Bath today .. anyone on here?
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We (Mrs SteveD and myself) were in Bakewell and Matlock last week. We went to the Bakewell Pie Shop
Need a Bakewell Tart emoji here 
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Like this you mean?
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Nah. These were 6" in diameter ( and impossible to eat in one go)
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Ah, one of those Bakewell Tarts.....lovely
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Still trying to work out which pudding shop is the original one ...Tim (rozabikes) will know ... his shop is in Bakewell I think..Word is never call them pies only puddings!
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Like this you mean?
That is a travesty not a bakewell cake.
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"Travesty" is a bit harsh, technically it's just an iced bakewell tart surely! Or are there Bakewell purists that are going to argue it's a pudding and shouldn't be covered in fondant icing? Surely Mr Kippling couldn't get it that wrong?
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They are totally different to the Mr Kipling variety ...an acquired taste... loads of lard in them and bitter almond taste .. you will get acute indigestion if you wolf too much of one down DAHIFKT.. evidently a cook at the nearby Rutland Arms Hotel cocked up on a pudding way back when but served it up anyway and it took off from there. WHERE is Tim (rosabikes) !! he should be writing this ... I should be talking Cod & Haddock !
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Like this you mean?
is this a KO tart? or later K2 pudding ??
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Isn't the pudding the earlier model?
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They are totally different to the Mr Kipling variety ...an acquired taste... loads of lard in them and bitter almond taste .. you will get acute indigestion if you wolf too much of one down DAHIFKT.. evidently a cook at the nearby Rutland Arms Hotel cocked up on a pudding way back when but served it up anyway and it took off from there. WHERE is Tim (rosabikes) !! he should be writing this ... I should be talking Cod & Haddock !
Here I am but no expert on tarts etc. However Bakewell puddings and tarts totally different things. I am advised the "original shop" is the one on the Sheffield road side of town opposite bank of Scotland. Hate the things personally by the way. Give me a eccles cake any day! ;D
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I was there a couple of weeks ago.
That bank caught my eye.
Here's why:
(https://uploads.tapatalk-cdn.com/20170908/dde0b5cd529899853e2229c887eea841.jpg)
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One of few banks left in town that. Closing left right and centre. A relatively old demographic in Bakewell with many retirees, not up with internet banking as alternative offered. I will soon have to drive 8 miles to Matlock to pay in any business cheques when Lloyds too close in a month or so! What ever happened to customer service?
Whats that got to do with cam lobes anyway? Sorry rant over!
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Still off topic but anyone visiting they do a really nice breakfast in the Pudding Shop, The Square, Bakewell DE45 1BT (not the original I know Tim) with good WiFi so you can tune in to what's going on here, after you have finished it. Lovely lady who runs it too. Also there is a quaint old second-hand bookshop near to the river that is really good (think it funds the local bus transport for old folks)... I got a 400/4 service manual from there for £2 and they have some really interesting old books in there. If you park in the big car park just out of town (loads of space) then you can get £2 back if you spend £15 in the Co-Op. Just love Bakewell every time I stay at my bro-in-laws cottage.
Back to the cam ... I will get hold of my K4 cam over weekend and measure it as promised !
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Cheers AshimotoK0! Interested to see how it compares with mine!