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  1. #1
    the-chauffeur's Avatar
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    Valve clearances - '72 SL350 cam/rockers in '69 head

    I'm running '72 top end internals in a '69 case, and on the basis that I'm using rockers/camshaft/cam sprocket/end caps and so on from the newer bike, I assume everything should be fine (the outer case is essentially the same for both models).

    However, having adjusted the clearances and cam chain tension and balanced the carbs as best I can, the top end sounds more noisy than it used to when I was using the original cam/rockers. I know the cam design of the later models makes them more peaky, but I'm not sure whether that would change the sound from the top end.

    So 2 questions - are the valve clearances the same between the models and are the clearances quoted in the book the optimum settings or (as they are in the 750 Haynes manual) the maximum settings?

    Thanks in advance.
    SL350 K0 (1969)
    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

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  3. #2
    Super Moderator outobie's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    I wouldn't have switched your cam sprocket...wear items need to stay together as a matched set, chains and sprockets in this case

    I would have kept the cam box, end caps, cam, rockers, rocker adjuster pins all together, form the 72 and used the cam chain and sprocket from the 69

    I would have also picked the best cam chain tensioner and guide parts from the two,

    how were the valves? did you test them? to see if they leak?, how are the valve guides?...any play?

    did you set the valve lash properly? did you set the cam chain adjuster properly?
    did you measure the cam end play and get it within spec?
    did you make sure the oil passages are clear and not blocked by improper gasket placement?
    all of the above will add to noise
    CB350 K5 - Uber Café- Engine build 3
    CL350 K4 - Cafe build done waiting on final assembly
    CB350 K0 - Full restoration w/Hondaline bags & fairing
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  4. #3
    the-chauffeur's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    Thanks chap.

    In order:

    Cam sprockets aren't interchangeable between early '69-'72 camshafts - they cutouts in the centre are different shapes for the different lobe grinds/angles. Cam chain, tensioner and wheels had less than 150 miles on them from brand new.

    Can't remember whether I used the matched adjuster pins and end caps. Cam box remained unchanged, although I found and corrected one of the reasons the earlier cam/rockers got trashed - 2 oiling holes were never machined out properly.

    Valves were fine. When I rebuilt the head last time (150 miles ago . . . ) the seats were recut and valves matched. Guides were fine and no leaks.

    Lash? If you mean gap, yes, set properly, as was engine timing; ditto the camchain adjuster. End play was in spec after I replaced the 0.1mm spacer that got trashed when it snapped and wound itself into one of the the original end caps (the other reason the top end needed changing). I still don't understand how that happened.

    Oil passages as above, although I also modified the cylinder base gasket to remover the material that sits over the oiling holes (the gaskets come with circular cut outs for the cylinder studs whereas the rear external stud-and-oil holes are teardrop shaped). Oil flows out when the 10mm head bolt on the top LHS of the cam box is removed. Gaskets showing no signs of leakage, and I was very careful about orientation of the two that sit between the end caps and the cam case.

    Thinking about it, the only major difference between this build and the last was the use heavy duty cylinder studs, which are the same diameter their entire length (whereas the originals have wider ends than centre sections). The vendor - who makes/sells performance parts - assured me the studs didn't require any mods to the oil passages, although I guess they might be a little more restrictive than the originals (oil flow wise).

    And that's kinda why I'm scratching my head.
    SL350 K0 (1969)
    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  5. #4
    Super Moderator outobie's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    Quote Originally Posted by the-chauffeur
    Thanks chap.

    In order:

    Cam sprockets aren't interchangeable between early '69-'72 camshafts - they cutouts in the centre are different shapes for the different lobe grinds/angles.

    true; but a dremel will open up the cutouts in less than a minute

    Cam chain, tensioner and wheels had less than 150 miles on them from brand new.
    now you have 3 different wear conditions which need to seat themselves together New chain, crankshaft sprocket from the '69, cam sprocket from the '72...I'm sticking by my original statement of keeping the 69 sprocket in the head...at least that only needs the chain to work into a set of sprockets with the same wear

    Can't remember whether I used the matched adjuster pins and end caps. Cam box remained unchanged, although I found and corrected one of the reasons the earlier cam/rockers got trashed - 2 oiling holes were never machined out properly. a picture of the holes you drilled will be interesting. I've not come accross any manufacturing defects personally but I've heard of them from time to time.

    Valves were fine. When I rebuilt the head last time (150 miles ago . . . ) the seats were recut and valves matched. Guides were fine did you actually measure for side play? and no leaks.

    Lash? If you mean gap, yes, set properly, as was engine timing; ditto the camchain adjuster. End play was in spec after I replaced the 0.1mm spacer that got trashed when it snapped and wound itself into one of the the original end caps (the other reason the top end needed changing). I still don't understand how that happened.

    Oil passages as above, although I also modified the cylinder base gasket to remover the material that sits over the oiling holes (the gaskets come with circular cut outs for the cylinder studs whereas the rear external stud-and-oil holes are teardrop shaped). Oil flows out when the 10mm head bolt on the top LHS of the cam box is removed. Gaskets showing no signs of leakage, and I was very careful about orientation of the two that sit between the end caps and the cam case.

    Thinking about it, the only major difference between this build and the last was the use heavy duty cylinder studs, which are the same diameter their entire length (whereas the originals have wider ends than centre sections). The vendor - who makes/sells performance parts - assured me the studs didn't require any mods to the oil passages, although I guess they might be a little more restrictive than the originals (oil flow wise).

    these engines run low pressure oiling systems so I wouldn't expect trouble from the fatter studs
    And that's kinda why I'm scratching my head.
    I can't really poke any holes in what you've described. the cam gear / chain could account for a bit of the noise.
    are you certain the cam sprocket bolts are properly torqued and locktited in? If in fact you did use the 69 end caps with the 72 cam there may be some noise as the cam wears into the new bearings. did you happen to measure the cam bearings to see if they were in spec? any noticible scoring on the end cap bearing surface?

    could also be that you're just paying more attention to the noise so it seems louder

    by the way the valve adjustments are the same for all years...
    .05mm intake
    .10mm exhaust

    are you experienced with telling how to properly use feeler gauges to get the proper resistance when checking gap? the spring retainer caps stick up just a tad higher than the valve stems so your feeler gauge encounters some added resistance from the retainer caps since it rubs them getting to the valve stem....one trick I use when setting valves is to tighten the adjuster with the feeler gauge in place just so that I can't remove the feeler...then loosten till I can move the feeler again.

    you did remember to check/set your valve lash (clearance) with a stone cold motor? I never try to set unless the motor's not run in at least a day.
    CB350 K5 - Uber Café- Engine build 3
    CL350 K4 - Cafe build done waiting on final assembly
    CB350 K0 - Full restoration w/Hondaline bags & fairing
    SL350 K2 - Bubba Shobert flat track build on deck
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  6. #5
    the-chauffeur's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    Thanks Obie

    Good point about the Dremel on the sprocket. Why hadn't I even thought about that?

    The cam box was a weird one, and with 7,500 miles on the clock and no real previous trouble before I got it, I'm not entirely sure whether the oil holes that weren't had anything to do with the last set of problems I encountered. Anyways, since the bike's purchase, I've bought another couple of later SL heads secondhand for various components and compared them with the early one. All have the same oiling holes (one inside each hole for the eccentric adjusters), although the earlier heads have a different part number - so I was wondering if that had something to do with it.

    So, my early cam case only had two properly formed holes by the rear adjusters; one other had a partial, the fourth was virtually non-existant. Poking around it was clear the casting was flawed because the walls in the areas where the holes should have been were paper thin. I just worked them clear with a toothpick and tidied them up carefully with a drill bit. If I remember, I'll get a photo of what I'm talking about from the '72 head I'm working on.

    TBH, I didn't measure valve side play, but IIRC the valves were new, and the guides were reamed at the same time as the seat were cut. I certainly measured the camshaft sideplay - and put plenty of oil on both it and in the side caps before bolting together. After the incident with the busted camshaft spacer, I've treated the '69 end caps as trash. The caps have been replaced with some others; whether they matched the camshaft, I can't be 100% sure.

    Valve clearances may be where I've got it wrong. Yes, I'm usually OK with feelers, but I'm perhaps overly conscious of how the bike responds after the disaster last time. Stone cold, yes. Done right . . . well . . .

    . . . let's cut this very short. The local Honda shop asked if they could borrow a couple of my bikes (inc. the 350) to show - they had a couple of Honda Superbike Team riders turning up for an evening event. As a thank you, they said they would have a look at it, and when I fired it up, they immediately said they thought it was valve clearances. One of the lads there cut his teeth on 350's, so he's going to give it a once over.

    So thanks again for the pointers. I'll report back when I know more. Meantime, I've got a 450 top end to reassemble, and then I'll start on the other SL350 . . .
    SL350 K0 (1969)
    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

  7. #6
    Super Moderator outobie's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    if memory serves, the slk0 heads were the same as the cb/cl but the K1 & K2 had smaller intake ports, hence the different part number.

    it will be interresting to hear what the shop guy has to say on your valves...a little loose is noisey but better than having them a little tight...also the racers run them a bit looser than stock to help prevent valve float at high RPMs.
    CB350 K5 - Uber Café- Engine build 3
    CL350 K4 - Cafe build done waiting on final assembly
    CB350 K0 - Full restoration w/Hondaline bags & fairing
    SL350 K2 - Bubba Shobert flat track build on deck
    CB-1 400F - unrestored mint rider
    2012 Guzzi V7 Racer - Daily Ride

  8. #7
    the-chauffeur's Avatar
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    Re: Valve clearances - '72 SL350 cam/rockers in '69 head

    Yeah - I'll be all ears (!) when I pick it up.

    The different part numbers I was referring to are those for the cam cases (as opposed to the lower sections of the heads). I can't see any physical differences between those parts, which may be why the later ones simply superseded/are interchangeable with the earlier ones.

    Strange one, that.
    SL350 K0 (1969)
    SL350 K2 (1971)
    CB450 K6 (1972)
    CB750 K2 (1972)

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