1965 Matchless G15-CS


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Also, compression hot is 151 RH and 144 LH. Seems close enough/high enough that it shouldn't be any valve issues or major imbalances in the cylinders, right? Guess I wasn't done fucking with it.


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140-150 psi is plenty high and the 7 psi delta is nothing to worry about IMHO.


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I think my next move is once again de-mounting carbs, de-mounting head spacers, cleaning/sanding all to confirm flatness, cleaning the head, and re-mounting with fresh Hylomar to get a good seal everywhere.


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Hopefully, tomorrow morning all the crud can come off the flanges and spacers and everything dressed and put back together with some fresh Hylomar to seal up tight.


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Forgot about those before I put the fuel tank back on, lol. Next time it's off, maybe.

Got the carbs and spacers cleaned, dressed, and reassembled easily. Discovered a poorly-feeding master carb; when the fixing bolt is too tight, it won't flow. Found a throttle cable issue that was in fact pulling at times, but not always, which had made it hard to find.

Seems like it wants to run now; took a spin and the mid-range felt amazing round the 'hood. Alas...FUCKING TACH DRIVE BLEW THE RIGHT SIDE COVER OFF AGAIN!

I don't know what I'm doing wrong with that thing. Maybe it doesn't need any grease at all??


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(Pre-full-cleaning gears)

Well, I can't find any flaws with the gears or the tach body, so I cleaned thoroughly and reassembled, this time with vastly less grease in a less-stiff variety, and repoured epoxy over the covers to hold it together. Hopefully there's no more gear ejection. If there is, I'm going to get a repop unit from Speedograph while the exchange rate is favorable. Allegedly they're made of NOS Smiths parts.


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While reinstalling everything, I found the drive spade on the cable bent, presumably from the poor position of the original (to me) timing cover and the way the cable ran over the pipe.

Replaced, bent the spare back to straight, re-greased the cable staying away from the instrument head, and ran it for a while...much less cable vibration, more consistent RPM reading, no gears ejected. I think I found the combination of things making it go boom. (He said, waiting for the needle to sink to zero over his next ride...)

Otherwise, idle mix still needed adjusting but that's ongoing...bike is RIPPING on the road. Front brake definitely needs attention now...soon as I pick up flux from Grainer I'll shorten the cable for starters. (Stoppers?)


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^Running snortier than ever. New plugs were necessary, among other things. It loves the new timing advance and the carbs finally seem balanced.


Put on new handlebars and levers. Bar shape is better for me. Old levers had lots of flex due to the design and it made the pull even harder than it needed to...you were bending metal along with pulling cable. Got re-pop Amal designs (with adjusters at the bars, even!) and found fitting them was slightly problematic due to the need for a longer inner wire. Had to modify my new brake cable, along with dealing with incompatible threads at the adjuster on the brake plate. Got the clutch cable to *barely* fit as-is by screwing down the gearbox adjuster and removing the handlebar adjuster nut entirely.


Drilled and tapped handlebar for the light switch. Thankfully an M3 screw works fine here, rather than obscure brit threads.


I also put on the finned valve covers because the tank was off again. Exhaust only, however...the intake cover couldn't come on and off with the carbs in place, so that's a no-go for both initial install and valve adjustment purposes. Kind of a business in back, party in the front situation. )

Just have a cable nipple to solder here and will be hopefully ready for some significant test riding tomorrow.

Ed: And done

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Spin up the road was magnificent. Felt like a totally different machine between the engine performance, braking, and posture/controls changes.

There's a stubborn throttle cable issue I have to sort before it's prime time, though. I've lubed them and it works just fine with the bike off...slides snap back really sharply every single time I let go of the throttle. I can't figure out what's going on while the engine is running...

Edit: Eureka moment at 4am while failing to digest a pound of cheese found atop the French onion soup we made last night. It must be the cable splitters that are causing the throttle issue...they work fine but are (were) likely moving around while the bike was running, catching on the frame or each other (choke and throttle run parallel) and causing the inconsistent problem I was facing. Woke up, lashed them to the frame top tube with some self-amalgamating tape and a zip tie for backup. Feels fine at rest but can't test till open-pipe hours start in my neighborhood. With this being the one sunny day this week, I'm going to get a solid test ride in.
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So, the throttle problem was twofold... throttle housing allowing twistgrip past the zero position under hard use, leading to the cable popping out the bottom and perversely hanging up enough inner wire to put it at like 1/3 open. Ordered new throttle. Did this to keep the cable in place till it arrives.

But the engine was still starting to lean out over the course of every ride, getting to the point of no fuel in carb at all. Coupled with my throttle issue the engine was just skyrocketing through the revs...kill switch would barely cut it off. After chasing through sticking carb needles (since applying the tickler didn't give me a gush of fuel) and tank cap vents, I found the cause.

Nice new Tygon fuel lines get even softer and droopier as engine warms up. They start to sag and kink. First I splinted them at the carb using some big 3/8" fuel line, which helped but only forestalled the inevitable.


Turns out I just had to put the old lines back on and voila, nada problemo. The whole Tygon setup was just drooping on itself and kinking up.

Of course, because I am me, I also lost the oil tank cap a ride or two ago, possibly while flogging it back to life by the side of the road on the last test. So this got me through today's test with the new fuel lines; sushi takeout to the rescue. Replacement to arrive with the new throttle on Monday.


But today's ride was spectacular. Weather, local VA scenery. Blew past the CIA HQ at around 85 but the carb got a little balky at WOT. Maybe needs that float bowl extension after all.

Certainly the brakes are performing much better with the new cable, but going fast is an exercise in nerve even with them working well. Might put a twin-leading-shoe brake plate up front if I ever plan to use it in anger.

But for today, burbling along at 45-50 most of the ride with nothing to prove and a big grin may have been one of the best rides of my life.


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Weather was crazy today. Test drive showed carbs still need some minor tuning but the tach drive seems to be holding finally. (Now sans nickel, which detonated with the last tach drive. Spaced it out a bit from the timing cover with another paper gasket and thin washers under the mounting flange, plus less grease inside which I think was building up pressure at higher RPMs.)

New fuel plumbing and petcocks along with the carb refresh.

Now waiting on slightly richer pilot jets.

View attachment 224739
Great looking machine:cool:


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Well, I have been off the board for a bit getting ready for my move down south. Alas, my final ride in this area showed there's an issue in the LH cylinder after all. Oil fouling on the plug and seeming to be some seepage from the head/barrel junction, so once I have the bike back, I will need to get in the top end and see what's going on there.

Thanks for the kind comments and dreaming of being back in the saddle again...


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Canyoncarver, also, I put those Norton rebuild videos onto my hard drive to watch during quarantine. Thanks again!

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