Valve adjustment question.

10drum · Jul 2, 2020

Well, I adjusted the valves on this Norton I've been getting on the road. I adjusted them to the specs for a combat engine. .010" exhaust, and 0.008" on the intake. I found the intake set too almost zero clearance, the exhaust was a loose .010". Now the bike doesn't want to idle properly, it's acting like it has worn slides. The carbs are new. I'm going to go back in and double check. I was curious why so tight on the intake?

It has a Boyer, and I have the timing set just the way I set the boyers on my triumphs, they advance just to the mark. The compression is 160# on both jugs.

Thanks for all replies.

Fast Eddie · Jul 2, 2020

10drum said:
Well, I adjusted the valves on this Norton I've been getting on the road. I adjusted them to the specs for a combat engine. .010" exhaust, and 0.008" on the intake. I found the intake set too almost zero clearance, the exhaust was a loose .010". Now the bike doesn't want to idle properly, it's acting like it has worn slides. The carbs are new. I'm going to go back in and double check. I was curious why so tight on the intake?

It has a Boyer, and I have the timing set just the way I set the boyers on my triumphs, they advance just to the mark. The compression is 160# on both jugs.

Thanks for all replies.

Triumph man huh...

You know the cam goes backwards in these Norton’s right...?

You wouldn‘t be the first Triumph guy to trip up on that...

10drum · Jul 2, 2020

Eddie, how's the whatever those letter on txt are called? ROFLMAO (rolling on floor laughing my ass off).

When all else fails, read the instructions. I love working on these bikes. Glad I said something about my triumphs.

THANKS.

10drum · Jul 2, 2020

Eddie, there's a bar near St Louis called Fast Eddies. Great place, cheap food, cold beer, and usually good bands.

Flatspot · Jul 2, 2020

My old 6t was easy to set the clearances - zero, warm just allow the pushrods to turn. Was it ramp cams they were called?

Triton Thrasher · Jul 2, 2020

Landspeedracer said:
My old 6t was easy to set the clearances - zero, warm just allow the pushrods to turn. Was it ramp cams they were called?

Ramp cams (E3275) got 0.010” clearances.

The cams on 5T and 6T Triumphs before the ramp cams had 0.001” clearances recommended, which would be more or less just free to spin.

Flatspot · Jul 2, 2020

Thanks, this was 40+ years ago and I don’t remember a lot of what I got up to back then

Triton Thrasher · Jul 2, 2020

I tuned my T110 a step too far when I got big inlet valves as well as E3134 cams. Lost low-end useability and midrange pull.

Rather unbelievably, 0.008” valve clearances fixed it.

ashman · Jul 2, 2020

My mate runs a Joe Hunt Maggie on his 650 Triumph the same as I run on my Norton, his points are shot on his Maggie and he knew I had a new set for my Maggie and asked if he could use them while he ordered a new set, I told him they won't work as the Triumph runs clock wise and the Norton runs anti clock wise, after 8 years running the JH the point's are still like new with over 30k miles on them.

Ashley

10drum · Jul 2, 2020

I went back and checked the clearances that I set earlier today. They are right on the specs for the Combat engine. Now, here's my new question. Is this a combat engine? The "C" is on the head. There is a vent at the back of the crankcase.

Why was the inlets set to near zero. Does this bike have a different, or worn cam? How would I tell without pulling the top end?

Anyway, I adjusted the intake to a .006, left the exhaust at .010, ran much better. I wouldn't thought that would've made much difference?? I suspect this engine may have had the "combat" taken out of it. I'm going to tighten the exhaust to .008 tmr, see what happens.

motorson · Jul 2, 2020

I really can't think of a reason why a loose valve would make much difference in how an engine runs. A tight valve will make a big difference though. I assume that the grind of the cam as well as the heat of operation on a Combat is the reason for the higher valve lash settings. I would go back and keep checking your valves for a few thousand miles because there is a good possibility that the tight valve got carbon deposited on the seat which will now wear off because it is actually seating each time. If carbon is wearing off of the seat then that valve will tighten up a bit. If it stays the same then there wasn't carbon on the seat.

You can check the compression by filling the cylinder with oil at TDC measuring it as it goes in. Then devide the total displacement plus the volume of oil by the volume of oil. A Combat should come out to be about 10.5 to one. You can also look at the bottom of the cylinders and at the head gasket to see if any one put a spacer in there to lower compression.

Triton Thrasher · Jul 2, 2020

motorson said:
I really can't think of a reason why a loose valve would make much difference in how an engine runs.

Because a bigger clearance makes the valve open later and close earlier.

Triton Thrasher · Jul 2, 2020

10drum said:
Why was the inlets set to near zero.

Why do people do things wrong?

Big question!

Fast Eddie · Jul 2, 2020

Unless there is a spacer under your barrels, or a much thicker than stock head gasket, a ‘C’ head most likely means you got higher compression. The only other way would be someone fitting special pistons, which is a low probability.

The Combat also had what was essentially a race cam. Best way to check this easily is to remove the rocker covers (again), and plugs, and by turning the engine over, carefully measure the valve drop. If it’s a stock cam, the inlet and exhaust valve drop will be the same amount. A Combat cam (or 2S) has a higher inlet lift than exhaust.
At least this will tell you if you have a 2S cam and therefore need to use the Combat valve clearances.

My guess on the tight tappets is someone torqued up the head gasket, crushed the gasket a little, and didn’t check the tappets...

Fast Eddie · Jul 2, 2020

Triton Thrasher said:
I tuned my T110 a step too far when I got big inlet valves as well as E3134 cams. Lost low-end useability and midrange pull.

Rather unbelievably, 0.008” valve clearances fixed it.

Dave Degens told me years ago that opening up the tappets on hairy Triumph cams will reduce duration and therefore improve the bottom end / mid range. So we’d use different tappet clearances for different tracks.

In reality, such fine tuning was wasted on a numpty like me, but it felt good doing it!

We also used different cam timing for different tracks.

dynodave · Jul 3, 2020

Seems most/everyone except TT are missing the important characteristic of the 2S cam.
The RAMPS!
http://atlanticgreen.com/images/cam120.gif
If you set the clearance tighter it has a very big effect on duration degrees, though not effective lift is less so. Opens way early and closes way late.
When a few tho too big the duration degrees increase is almost negligable.
A"combat" is a specific list of components and any one item different or missing make is other than a real factory combat. IMO

Nortoniggy · Jul 3, 2020

As Dave alludes to, it's the camshaft type that dictates the correct valve clearance setting. The type of head or compression ratio don't. Given the age of these bikes, unless you've had the engine apart it's anyone's guess what cam is in there.

10drum · Jul 3, 2020

Fast Eddie said:
If it’s a stock cam, the inlet and exhaust valve drop will be the same amount. A Combat cam (or 2S) has a higher inlet lift than exhaust.

Thanks Eddie. I don't have a dial indicator. I used a straight edge and a depth gage. I'm not sure what difference of drop there would be on a combat cam, from a stock cam, but it appears I have the same amount of drop.

Fast Eddie · Jul 3, 2020

This was discussed in another thread recently where it was stated:
“The valve lift (not cam shaft) as measured at the tappet end of the rocker is 0.441 on the Combat, 0.375 standard for the inlet valve. The exhaust is 0.391 vs. 0.375”

So, you should have 0.050” more on the inlet.

Full thread is here:

A late 72 journey out of hibernation (2020)

Sounds like mine was acting before it went into orbit. It was the drive though. Yeah I pulled lubed cable (have a new cable here now) and tested with a drill speedo is fubar. Anyone got some good rebuilder references? First quote was $280 thought that bit much, glass, gauge face and odo all good.

www.accessnorton.com

10drum · Jul 3, 2020

Eddie, I understand, I should've wrote, what the difference of drop would be, as a result of the combat cam. You gave me the info I needed. I am confident that the way I measured the drop, I was within .010". I would've notice a .050" difference. This bike has a standard cam. I have set the clearances to standard. I'll let you all know after I run it. Thanks.

Valve adjustment question.

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