1974 CT70 Cam Timing and Ignition

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nanaimogreg

Member
Ive been working on trying to get my 74 CT going for a while and am working my way through what could be preventing it from starting. I am troubleshooting the carb and appreciate the advice members have provided (Also see my other Thread regarding Carb Troubleshooting).

I thought I would start a separate thread regarding how to properly set the cam timing and general ignition system because it doesnt fit with my other thread.

So I rechecked my recently installed points tonight to ensure they were set correctly. When checking your points how exact do you want them. Should they just barely start opening at the F mark? I'm confused because you need to set both the gap and when the points open at the same time. Can I assume that with new points if they open at the correct time (at the F mark) that the gap will be correct? What procedure works best for you?

I also rechecked my valve clearances and set them according to the manual.

When I removed the cam sprocket cover to check if it was in time and had not skipped a tooth this is what I saw with the engine at TDC on the compression stroke



. IMG_0287.jpgIMG_0288.jpgIMG_0289.jpgIMG_0290.jpg

As you can see the 'O' is not perfectly lined up but its close. Also the chain seemed a bit loose and made a bit of a funny clicking sound as I slowly turned the flywheel and it looked like it was tightening and loosening. It looked like this:
[video=youtube_share;sfplw-1wWTs]http://youtu.be/sfplw-1wWTs[/video]


I tried to better align the 'O' with the notch and this is what it ended up like:

IMG_0292.jpgIMG_0293.jpg
I inched the sprocket down a tooth on the chain while keeping the flywheel on the 'T'. The bolt holes in the cam side had to be lined up with the sprocket meaning I had to turn them to line them up . Not knowing much about engines would this cause any problems? The 'O' still doesnt line up perfect but its close. Seems like its about half a tooth on the opposite side of the notch than it was when I started. Is this better or worse?

I reassembled everything and tried to start the bike. As stated in my previous post I havent had much luck starting the bike and pending carb issues that I am still working on (waiting for parts) as expected the bike still did not start. This time however, I got a loud pop/backfire coming out of the muffler that did not happen before and the spark plug
which is brand new looked black.

IMG_0295.jpg


My question is: Based on what I have shown and described does it look like the timing should be ok? Also what could the backfire and black spark plug be from?
 
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b52bombardier1

Well-Known Member
That plug probably will not fire because it is likely now conductive across the formerly white insulator. The spark simply drains across the oily film rather than arcing.

You are either terminally rich with the fuel mixture or you are leaking oil from a valve seal. There is also an outside chance that you have a bad oil control ring on your piston. All of these items are repairable.

Was that a new spark plug recently installed?

Rick
 
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kirrbby

kirrbby

Well-Known Member
Did you reset the points after you moved the cam chain? I'm not positive but I think your timing mark set just below the mark on the head is preferable. You can adjust the cam chain tension manually on a 74 by removing the, 14mm (I think) nut that's just under the shift shaft, then loosen the locking nut with a slotted stud then tighten the adjuster thats in the hole where you removed the 14mm. Lol long sentence. Hope that makes sense. The locking nut locks the slotted stud, to clarify, the stud is basically a set screw for the cam chain adjuster. Back the stud off before turning the adjuster. You should search for a service manual.
 
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nanaimogreg

Member
b52bombardier1 said:
That plug probably will not fire because it is likely now conductive across the formerly white insulator. The spark simply drains across the oily film rather than arcing.

You are either terminally rich with the fuel mixture or you are leaking oil from a valve seal. There is also an outside chance that you have a bad oil control ring on your piston. All of these items are repairable.

Was that a new spark plug recently installed?

Rick
Click to expand...

Yes that was a brand new spark plug. The bike has not run more than 60 seconds with it so far.
 
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ctbale

ctbale

Member
Your on the right tooth
that sound is normal ... well its normal when your chain is very loose. thats the noise of your cam when your rocker arm is just going over the high spot, then rotating your cam because your chain is has play. I can see the play on the vid (oh, awesome vids and pics!!) the chain will snap when you hear the noise.

This is how I adjust chain tension. you need a 12mm and a 14mm wrench, flat blade screw driver and I use a 1/4" extension.

get eng tdc comp stroke
take the "alt drain" plug out with the 14mm, dont loose the washer
use the flat blade and uncrew the spring retainer, a little oil and maybe 1 or 2 springs will fall on your rag I forgot to mention.
unscrew the 12mm lock nut about 2 full turns (or just take it off)
then unscrew the set screw 1 turn,
I like to see the tensioner rod come out on a "new to me" bike, so I can check for corrosion and verify the beveled side is facing me.
if it does not fall out, you and help it out by pushing on the chain near the cam, or by turning the engine over a little, that will get it moving.
check that the rubber "HEAD" is on your rod, and that its actually still rubber!
then, at tdc, and the bevel facing you, I use a 1/4" extension or a phillips screw driver and push that rod up with "pinky force" and set the set screw. thats the right tension. sometimes I just shove it hard, and release the pressure a bit., but you cant over toighten your chain if you use your pinky. unless your super strong.
put it all back together, you done with your chain.

I check the points with a meter (electrically) , thats the only way to get it spot on. The coil doesnt care about gap, dwell is a function of how new the points are. The coil only cares about when the points "crack" open, cuz thats when the all important spark occures
 
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nanaimogreg

Member
Pulled the stator plate to access and check the cam sprockets and chain. Do these sprockets look worn to you?

IMG_0422.jpgIMG_0423.jpgIMG_0424.jpgIMG_0425.jpg

Can you remove the oil pump sprocket without splitting the case? Also is it just the one bolt to remove the upper cam chain sprocket?

With the cam chain tensioner, should the shaft be able to move up and down by hand? Note in my photos the head and cylinder were both removed so the cam chain was really loose.

IMG_0424.jpgIMG_0425.jpgIMG_0426.jpgIMG_0427.jpg
 
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