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Discussion Starter · #1 ·
Hi-- I'm new to the forums and have a '71 CB450 that I picked up a few months ago. It has been difficult to start and idles poorly, and I decided to do what is probably much overdue maintenance and I plan to replace the battery, coils, condenser, points, and plugs-- so basically re-do the ignition system and time the points, etc. I have the parts in hand but my understanding is that I should do a valve adjustment and then a cam chain adjustment, and THEN with the new ignition parts install everything and finally do the timing step.

So here's where I'm stuck. I can't figure out how to do the whole valve adjustment step. I have the full Honda service manual and they show the front or exhaust side cover off and the where the feeler gauge should go and where the adjustment screw and locknut is, BUT-- I can't seem to find anything about the intake side and that cover seems sort of buried by cables and a big black tube (sorry total noob on this bike) attached to what I think is the valve cover on that intake side?

Am I correct that both of these big rectangular covers (ie front and back or exhaust and intake respectively) need to come off and that I'd be looking at the same basic thing once I expose what's underneath? Then I'm measuring clearance with my feeler gauge, setting it correctly, closing it up and moving on?

I can't find anything on Youtube about 450 valve adjustment-- there is a great 350 video from CMC but obviously totally different arrangement with that bike.

Any help/advice/photos/video MUCH appreciated

Anyone in central or eastern Massachusetts area working on a bike like this? Would love to find a build partner-- if I can get this thing running would like to do a mild Brat coversion-- really just bars and maybe exhaust and seat-- possibly battery box and air filter conversion later.

Mitch
 

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Yes, the intake valve cover has to come off; the tube should be attached to it, as it is the crankcase pressure vent. The only other cables that should pass down over it are the throttle cables (one each carb), and the clutch cable, but, clearly, this is a much easier job if you drain the fuel tank and remove it. Be careful of the crossover fuel line at the back of the tank, which has to be remove from one end, and take the fuel lines to the carbs loose at the petcock.

BTW, there is a dedicated CB450 section below this one - more answers will be available if you search that section, and ask the experts there. http://www.hondatwins.net/forums/14-dohc-450-s-500-s-cb-cl-1965-1976
 

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It would be easier not only to remove the tank but the carbs as well. There really isn't a lot of space back there.
 

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Discussion Starter · #4 ·
OK -- I didn't see the specific forums-- duh on me--I'll jump over there with this question and future ones thanks.
I do have the tank off and I can see how getting the carbs out of the way will help too
Mitch
 

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OK -- I didn't see the specific forums-- duh on me--I'll jump over there with this question and future ones thanks.
I do have the tank off and I can see how getting the carbs out of the way will help too
Mitch
Or we could just move this one over to that area and delete the duplicate so there is no confusion and keep the comments in line. ;)
 

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Discussion Starter · #6 ·
OK thanks
I'll take off the carbs this weekend and free up the bolts on the valve covers-- at least three are pretty locked up so I have penetrating oil on them
Do you know what the correct bolts would be if I wanted to replace all of them with new ones? Would it make sense to go to an Allen head bolt?
 

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The bolts are either 6x28 or 6x32, depending on which hole they are in. Make sure you measure them as they come out, and mark the holes; if you use a longer one in a hole meant for a shorter one, you will crack the casting inside when it bottoms out. In my experience, the heads of socket-head bolts have less contact area, so I would recommend against them; they may be fine, though. YMMV

EDIT: Looking through the manuals I have, I think the intake side are all 6x28 and the exhaust side 6x32, but I'd still measure them.
 

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I take a pic of the area/ item I'm tearing into..print a copy, adhere it to some cardboard and put the nuts/ bolts on/in the pic at their corresponding locations..
 

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I cut a few threads off the two outer/lower bolts so I can get them out without removing the carbs. I remove the throttle cable adjustment perches and pop the barrel ends from their homes. Then if all goes well I don't have to rebalance.
 

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Discussion Starter · #10 ·
I seem to be able to get to all of the bolts but I see what you're saying about needing the room to back them all of the way out.

It does seem like even if I could get the bolts out of there I'd need to "Houdini" the cover out but maybe just getting the throttle cable out of they way will do it (it needs lube anyway)

Thanks so much WinterSol and Rob because I would have thown all of the bolts into a container-- the cardboard idea is inspired!

If I do get new bolts for some or all is stainless steel the way to go? Should I use anti-seize grease on the threads?

Sorry but any tips on the valve adjustment itself or just follow the Honda Shop Manual?

Thanks-
Mitch
 

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Honda CB350 valve adjustment procedure. A technique to adjust valves without a feeler gauge with a warm engine without removing tappet covers. can be done on the following late 60's early 70's Models CB450, CL450, CB500T, CB350, CL350, SL350,
 

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Honda CB350 valve adjustment procedure. A technique to adjust valves without a feeler gauge with a warm engine without removing tappet covers. can be done on the following late 60's early 70's Models CB450, CL450, CB500T, CB350, CL350, SL350,
I'd be scared of getting them too tight and the potentially bad results.
 

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I'd be scared of getting them too tight and the potentially bad results.
I agree, great way to toast your cams and followers if done wrong. I've heard many accounts of old Honda mechanics who used to use this method and no longer recommend it due to how imprecise and easy to go too tight it is. It is a pretty simple procedure to adjust the valves on the CB450, much simpler than on some modern bikes that require you to disassemble half the bike before you can even get to the valve covers.

Motorcycle Nut, have you ever checked your clearance with feeler gauges after this by ear adjustment and confirmed clearance is correct and consistent across all valves? or at least inspected base circles of cam to ensure follower is not in contact?
 

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Have a look at figure 3.25-b on page 22 of the fsm for the correct range of the clearance adjustments; you will find that there is another spot, outside that range, where the clearance will also reach the correct measurement, but that position creates incorrect geometry for the followers.
 

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Honda CB350 valve adjustment procedure. A technique to adjust valves without a feeler gauge with a warm engine without removing tappet covers. can be done on the following late 60's early 70's Models CB450, CL450, CB500T, CB350, CL350, SL350,
That's bad juju - you can get away with it on a 350, if you're experienced and careful.
I would NEVER attempt it on a 450, the dimensions are too critical............
 

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That's bad juju - you can get away with it on a 350, if you're experienced and careful.
I would NEVER attempt it on a 450, the dimensions are too critical............
You read my mind Bill - I've done 350s that way in the past, but 450s are just too tight a tolerance for that kind of method to be accurate, and the potential for a burnt exhaust valve or follower damage is too great to risk it if ridden out of spec too long
 

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I always use a .0012 feeler gauge to set mine. The .0012 feeler gauge can be hard to find. The closest SAE size is .0015. The .0012 inch is a standard .03 mm metric size. Find a metric feeler gauge that is marked in SAE, not a SAE that is marked in metric.
 

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I always use a .0012 feeler gauge to set mine. The .0012 feeler gauge can be hard to find. The closest SAE size is .0015. The .0012 inch is a standard .03 mm metric size. Find a metric feeler gauge that is marked in SAE, not a SAE that is marked in metric.
And yes, for those who aren't experienced with 450s or are just starting out - that IS the actual adjustment setting. Yes, it's tiny, the smallest sized valve adjustment setting of all Hondas with rocker arms/followers, but absolutely true. At the dealerships I worked, we used a long, automotive .0015" feeler gauge and rubbed a "curl" into the end of it to help get it around the cam and between cam and follower, allowing us to work both ends to pull it back and forth between the two parts to check the tension on the feeler gauge because of the lack of thickness of the gauge. I don't have that problem today myself because I'm running aftermarket cams that require larger clearances, but running .0015" on stock cams is perfectly fine (even .002" would be okay, but I wouldn't run them looser than that)
 

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And yes, for those who aren't experienced with 450s or are just starting out - that IS the actual adjustment setting. Yes, it's tiny, the smallest sized valve adjustment setting of all Hondas with rocker arms/followers, but absolutely true. At the dealerships I worked, we used a long, automotive .0015" feeler gauge and rubbed a "curl" into the end of it to help get it around the cam and between cam and follower, allowing us to work both ends to pull it back and forth between the two parts to check the tension on the feeler gauge because of the lack of thickness of the gauge. I don't have that problem today myself because I'm running aftermarket cams that require larger clearances, but running .0015" on stock cams is perfectly fine (even .002" would be okay, but I wouldn't run them looser than that)
Since the tappet (rocker) is disctincty unsymetrical, that 0.0012" at the cam/tappet junction translates to 0.002" at the tappet/valve tip junction. That's a much more familiar number to us Honda doods........
Many racers, including Hansen, regularly run up to 0.005" clearance, but I call it at 0.002" max.
I think it's almost impossible to set at 0.0012" for a normal human - especially since 450's tappet shafts invariably move around when tightening the shaft down, it can be very frustrating to try and pre-compensate for that movement.
I always clean/polish the washers behind those adjuster lock-down nuts, it helps to minimize that........
 
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