Valve clearance: Getting the shims back IN

tarrelbeer

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Hey forum,

Background:

Currently doing a lot of basic maintenance on my 1982 CB750f, my first post here was a few weeks ago and you guys were great help so here is another
question for my current problem.

Ever since I got this bike the idle has been 'hanging' high only when the engine is warm. I can bring back the idle to normal by engaging the clutch a bit. My first action was to check the intake boots on the carbs which were old, cracked and leaky confirmed with a carb cleaner test. Replaced the boots with OEM honda parts and this already made the bike run a lot better but the hanging idle persists.

I decided to check the valve clearance and try a carb synch (got one of those 4 meter tools) since thats probably a good idea to do anyways.

I checked the clearances, which as i expected were not great. i'd say only about half of the valves were acceptable clearance when taking 0.13mm (0.005 inch) as the benchmark. About 4 of the valves were actually so tight that i cannot even get a 0.05mm (0.002 inch) feeler gauge in.

Anyhow my question is:

Getting the shims out was not too hard with the special tool and a magnet. Getting them back in however? Absolute hell.
The shims constantly either slide 'over' the holder and to the other side requiring me to fish them back out, or they lay crooked on top of the spring with one side resting on the spring. Ive tried to insert the valve holding tool in different positions too but it does not seem to help.

Is there some kind of trick to this that i am not aware of? Ive been fiddling for at least 4 hours in total and only managed to get 1 freaking shim back in place.... very close to losing my patience.


I was wondering if this is a shared experience for you guys or if i might be doing something wrong.
 

amc49

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First of do NOT ROTATE THE ENGINE WITH SHIMS REMOVED!!!

The tool goes IN BETWEEN tappet PAIRS and holds 2 down at the same time. With the tappets collapsed there is no way any shim can rest on a spring as it is down out of sight. You insert the tool when the tappets are already rolled to compress springs as much as possible.

Done that way shims go in easier than they come out.
 

tarrelbeer

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Thanks for the reply!

I hope it's not the tools that's the problem, it's not OEM since that was not available where. I think I understand correctly how the tools works and I'm doing it exactly as you specified.

What seems to happen, just in case that I wasn't clear, is that I insert the tool and am able to press both the springs down at the same time. However, what happens is either:

- the shims just slides right over to the other side and I can't get in in place
Or
- the tool "blocks" ever so slightly over the top of the spring cause the shim not to fit and sit crooked

Hope this makes sense English is not my first language.

I'll fiddle with it some more but I don't know how this is supposed to be easy. Maybe my tool Is slightly off in size..

Sent from my SM-G950F using Tapatalk
 

tarrelbeer

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Update to close this thread: Turns out my aftermarket tool was not great for the job. Use original honda if available. Mine was both slightly too narrow and BENT. Making it very difficult to get the shims back in.

Unfortunately, every time i fix something on this bike, something else seems to break. I managed to swap the out the valve shims for all valves that were out of spec, but not all of a sudden one of the valves (Cylinder #3 exhaust) seems to be 'stuck' down and won't lift back up... :(

Is this a serious problem? Or can it be popped back with the right technique? Can make a separate thread if necessary, was not able to find it quickly using the search...

Any tips are very much appreciated.
 

amc49

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'I managed to swap the out the valve shims for all valves that were out of spec, but not all of a sudden one of the valves (Cylinder #3 exhaust) seems to be 'stuck' down and won't lift back up...'

You have bent a valve by turning engine too far or at the wrong time. You can't just turn them willy-nilly to set valves. One has to have worked on engines enough to recognize the danger points or when pistons are close, and you can even bend valves by hanging on the other one if not watching where you are at on the cams. You generally never feel the contact when paying attention to other things. They bend much easier than you think.

Or turned engine with no shim in a position to bend the outer edge of a tappet out to seize it up in the bore. Why I said what I did in post #2.

If valve bent then the tappet should still come up by fiddling with it, the valve under it won't though.
 

tarrelbeer

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Yup I'm quite a newb so I was probably in over my head for this task. Setting the valves om my CM400t was infinitely easier so I underestimated this one. Anyway, I appreciate your comments, can see that you answer quite a lot on this forum.

It appears that I slightly bent the spring with the 'bad tool' and it snapped back up together with the valve when it tapped it with a screwdriver.

When I put the covers back up, the bike did start and seeming ran okay but I only ran it for a few seconds.

Lets not celebrate too soon though because I might have still bent the valve I guess :/ .
 

amc49

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You can't bend a spring, they simply give to have something else damage. If it snapped all the way up you likely damaged the tappet (better) and now it will gouge out the hole in head while running.

Don't think it fixed itself no, no. Another rash decision. A tappet changed today may well save the engine..........of course, yours and do as you will.
 

user8086

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I've never had any problem at all with just a small pick small screwdriver small magnet, and the proper cam tool... never ever rotate that motor without shims in it.
 
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