Cam chain tension

Hi all,
What symptoms would you get if your cam chain was too tight. I have adjusted mine recently and when I did, took the slack out due to valve springs then set the play at aprox 3.5 mm total. That is up to down movement.
Bike is running like crap but I have been assuming its a timing issue. Timing was set at 31@5000rpm and 26@3500rpm as per Boyer recommendations.
Right on 4000rpm it misses then is fine from about 4400rpm but won't go beyond 5800-6200rpm.
Today, went for a buzz and 10-15mile in, totally powerless. Eg, flat road,50mph in 4th, just would not accelerate at all. Had to drop a gear but even still is struggled and misfired. Pulled over for a smoke then had another crack and small improvement was noted.
Returning home, missing badly intermittently until you give it a gut full.
Pulled the plugs, one plug lean the other rich. Single carb bike.
The things I have recently fiddled with are:
Timing Boyer removed
Cam chain adjusted
Timing refitted and set
Big bore mufflers fitted
Carb adjusted for the muffler change.

A tight cam chain. Other than premature wear I am not sure of any symptoms.

If your tappet clearances are all OK, sounds like one pot is not firing correctly. Swap the plugs over and see if the lean / rich changes sides. If yes, a bad plug, if no then, coil, lead, or low compression.

Wasted spark ignition and single carb really narrows things down.

Can't imagine a tight cam chain would lead to those symptoms. When setting the tension did you turn over the engine several times over to ensure you set the tension when the chain was at it's slackest? I have discovered that Norton didn't manufacture sprockets that were round/concentric so there are tight/slack spots depending on the sprocket positions.

Sounds more like dodgy wiring to the stator plate(?) under the points cover which is a common issue. - the wiring looks OK but tends to fracture inside the insulation. I believe that the solder connections to the plate can also fail. I drilled out the plate and put in two small bolts that I can screw ring terminals onto and renewed the last ten inches of wiring. When it failed on my bike the misfiring was dreadful but I nearly made it home...... until I had a puncture, aaarrgghhhh!

Any way, renewing those connections/wiring made a substantial improvement to the general running of my bike. It got even better when I did the nuts up that hold the carburettor on!!

Good luck.

3.5mm seems a little tight. I think more like 4.8mm or 3/16" is proper.
But your issue seem more like a bad plug, wire or coil.
The other tests may include battery and charging system along with a compression test.

"When setting the tension did you turn over the engine several times over to ensure you set the tension when the chain was at it's slackest? "

NO! You set chain tension (any kind of chain on any sort of machine) at the tightest portion of rotation. If you set it at the slackest, you risk breaking/straining the chain when it rotates to it's tightest position.

I don't see how too tight a chain would do this but sure can if chain too slack over all. Very similar power death occurred after Peel's tach needle disappearing act that wiped away the RMA tensioner - started and ran good until rpm over 4000 then barely could attain 5000 before power just poopoo'd to go above that on the level or trying to climb our small Mt's. Too tight a cam chain once heated can pull the pinon mount right out the case and/or jerk-fracture the oil pump snout drive snout and un form the tensioner shelf. If ya skipped a cog tooth it would likely lock up valve on piston trying to start.

Dkt26 said:

The things I have recently fiddled with are:
Timing Boyer removed
Cam chain adjusted
Timing refitted and set
Big bore mufflers fitted
Carb adjusted for the muffler change.

Click to expand...

What changes did you make to the jetting? You might want to go back to the original settings and just see what the bike actually needs.

There's a chance that you caused some damage to the wiring at the stator when you removed and re-installed it. The wires usually fracture at the zip-tie. The original design had posts. They saved $0.50 by deleting them. Make sure you have the rubber sleeve 061093 installed. It buffers the push and pull caused by the shaking of the motor in the frame. Check the resistance with a meter by shaking the wires, recheck the timing. It may have slipped.

mike996 said:

"When setting the tension did you turn over the engine several times over to ensure you set the tension when the chain was at it's slackest? "

NO! You set chain tension (any kind of chain on any sort of machine) at the tightest portion of rotation. If you set it at the slackest, you risk breaking/straining the chain when it rotates to it's tightest position.

Click to expand...

Aaarrggghhh, you are correct, I'd only just gotten out of bed when I typed that reply; apologies for any confusion caused!

Dkt26
Did you reverse the two leads at the stator plate?
I believe the Black Yellow; Black\White wires must be on the correct posts with the boyer. Double check. Go through the wiring diagram carefully and trace your wires back to the transistor box.
CNN

Did you reverse the two leads at the stator plate?

The symptoms you've been experiencing sound just like ignition not advancing and will happen if the trigger plate wires are reversed, I've had this myself and all symptoms disappeared when they were put right.

When you say you put on big bore mufflers, are they just larger pipes, or are they big bore through the muffler? If the hole inside the muffler is less than 3/4" and your running 750-style pipes, you're gonna have issues where it won't go over about 70 in a straight line or 40 or so up a hill.

too tight cam chain is bad, very bad

it can, and does, cause the spindle hole for the intermediate gear to elongate and cause rapid wear there

this happened to me when I had the spring loaded cam chain tensioner, I think I got it from RMA, something like that

anyway, when I had my motor rebuilt two years ago my guy, Jim Mosher (Performance Indian) was horrified to see the damage, insisted on rewelding the hole, refitting, and installed the original Norton slide tensioner.

The over big bore pipes I've experimented with made a dam dog down low only allowing some power over 5000, yuk, not your symptoms.

I've reversed Boyer leads but was pretty sure right off something wrong as ran rough misfiring on blip ups I didn't dare ride off. I've had the trigger wires break inside so only at some rpms they cut out - miserable boyer over sight that MUST be replaced by upgrades soon or later.

Over tight cam chain will give better valve control power - until things give way.
Almost everyone that has installed RMA spring ramp tensioner has really paid for it. sometimes twice, like me. Too loose chain is more power robbing than destructive.

Never hurts to try new plugs. Sometimes just enough water in bowls can bog as the fuel flow rises. Some time pettcocks just clog and stifle power. Once in a while its most of the above all at once.

Factory service release on cam chain tightness:

It is found that slackness of the cam chain can result in snatch, jarring shocks being delivered to the contact breaker and auto advance mechanism. This causes premature wear on these parts. We specify that the chain tension should be checked at 5000 mile intervals but, naturally, any obvious slackness evidenced by noise in this area should be taken up, irrespective of mileage. Adjust the cam change tension to between 1/8 and 3/16" slack (that is, up to down movement) on the top run of the chain. To do this necessitates removal of the contact breaker and auto advance mechanism (use the withdrawal bolt O6-0934 for the auto advance cam). Next take off the timing cover, and the cam chain and slipper tensioner are exposed. The oilway exposed by removal of the cover must be blocked by one of the timing cover screws (see owners handbook) to prevent the loss of oil. Note that chain tension can only be adjusted correctly if there is no play in the intermediate spindle.
To check the chain tension, remove the sparking plugs so that the engine will turn easily and use a 9/16" Whit. socket or ring spanner on the camshaft sprocket nut and turn slowly anti - clockwise so that the lower run of the chain will be kept tight on the slipper and a true check of the tension can be made on the top run.
In this way the spanner will control the alternating load of the valve springs on the camshaft and it will be easy to find any tight spot to which the tension should be adjusted as described.
To increase chain tension, slacken the two nuts securing the slipper and lift it a little at a time, checking at each stage after nipping up the nuts whether the tension is correct. When the correct tension is achieved secure the slipper nuts to 1801b. in (15lb. ft).
It is most important when refitting the timing cover to use the camshaft oil seal guide 06 - 1359 to avoid damage to the seal in the timing cover.

......"What symptoms would you get if your cam chain was too tight"..........."Too tight a cam chain once heated can pull the pinon mount right out the case" &...... "can cause the spindle hole for the intermediate gear to elongate", is all that came to mind. your rough running's gotta be something else.

This is not a big beefy chain and if it breaks, you're toast or at least your bike is. Other than that, I cannot think of how a tight cam chain could effect the general running of the bike. Too loose is another thing.

My bike had a wow'ed out spindle bore and setting the cam chain took many measurements and a calculator to get right. I got an old timing cover and chopped it to make the tool.

How the bore got trashed is somewhat of a mystery to me. The spindle does not spin and is held perpendicular with the timing cover. All I can think is that at some point someone wedge something in there somewhere to help remove the cam nut. As dumb as an act this is, it makes the most sense of how this could happen.

I eventually got a good set of cases, re machined and sleeved the spindle of the old set and gave it a good home.

Snapped points bolt and electrical short across the yellow/black and white/black wires.
Was real lucky with the points bolt. It snapped like a key and was able to remove the threaded section from the timing chest case with a little finnese. I thing the gods were happy to cut me a break for once.
Hey thanks for all the advice and help y'all.
Greatly appreciated.
Regards
Dave

Double refreshing to read, one something obvious we didn't guess prior and two that it didn't break other stuff. Next question is why bolt snapped - as trigger rotors have tapper to bind on shaft so its bolt only needs tight enough not to back off.

I think I know why it snapped. I was bein all NASCAR and using an electric drill with a clutch on it as a shortcut due to multiple adjustments. Even though the clutch was set to the lightest setting, I think the initial torque was too much for the bolt in the end. Mustn't have rally noticed on the last adjustment I made but sure found out when I had to remove it.
Moral, there are many shortcuts that will present themselves to you in your life, but not all of them will save you time.
Ps. I also have to retrieve one of the timing chest screws for the same reason. It didn't snap the head off the screw so it is functioning but it snapped one half of the screw head this rendering it no longer able to be undone with a screw driver.

Ok almost sorry I asked as no pleasure in your flash back of my own similar events, but I had to know so less chance I'd repeat your findings, being rather lazy and only slightly clever. I've fixed sheared off flush case screw with epoxy thread maker as too ugly a hole left getting out the screw.