1965 Matchless G15-CS

AgentX

Over 1,000 Posts
Seriously considering a single-carb Mikuni setup now, lol. But won't go there just yet.

If I do, I'd like a TM flatslide vs the VM.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
Another thing that just bubbled to the surface from long ago forgotten memories: Have you checked the timing on both sides with a timing light? I found a few cases in the past where the points cam was ground or located so that timing was different between sides. I had to stone them to get both sides to exactly match.
 

AgentX

Over 1,000 Posts
Another thing that just bubbled to the surface from long ago forgotten memories: Have you checked the timing on both sides with a timing light? I found a few cases in the past where the points cam was ground or located so that timing was different between sides. I had to stone them to get both sides to exactly match.


I haven't...it's not something I've ever done or am familiar with, but if the carb work doesn't help, I'll come back and ask how to do it. (Actually if you'd describe it or have a link, I'd appreciate it for general knowledge!)

The ring cam gives .001 difference in points gaps between sides, and appears to have ramps in the same shape, but it could be out from 180 or something. It's all new to me.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
What I have found in the past is that sometimes the ring cam is ground slightly incorrectly. What I had to do was to take a round wet stone. something like this https://i.ebayimg.com/images/g/ULYAAOSwDN1UTwhC/s-l300.jpg to gently grind down the higher lift cam. 1 though should be OK to work with. Then I attach a timing disk and fire up the bike and check timing on both sides with a timing lamp.

If one side is more advanced than the other, the cam has to come out and the lift face gently relieved. reassemble, re-test, rinse and repeat.

If teh timing is within say a degree or two, it probably isn't an issue.
 

AgentX

Over 1,000 Posts
Then I attach a timing disk and fire up the bike and check timing on both sides with a timing lamp.

That's the part I don't know anything about...I have never owned or used a timing light on a motorcycle. I have seen one used on a running car engine but this is a different thing entirely, I assume? The engine can't run with the timing cover off...the timing light would have to attach to the rotating mag points...right?

Sorry, I am just lost here with a metal timing disc and the closest approximation I can find of a cigarette paper...

The Boyer on my Enfield (coil ignition) I just set at TDC per the instructions then adjusted slightly in-situ while the engine was running to the best point.

Feel like a moron but really don't understand the procedure with a light.
 

AgentX

Over 1,000 Posts
Oh, and here are some carbs...


IMG_20200409_122233274.jpg


Since they are off, I will also take the time to install new petcocks, since I am currently lacking a reserve, and new fuel line/filter while I am at it.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
Awesome. Chopped monobloc. We used to add a float bowl extension to make sure there was enough fuel in that one bowl to feed both carbs at higher revs. Yes they are still available and look more or less just like I remember.

Timing with a cigarette paper, now that brings back distant memories. I'm sure Beachcomber remembers that. OK to run a timing light can only be done if you have access to one end of the crank and in this case that means the primary drive side.

Attach a timing wheel to the crank and use a piece of stiff wire from say a wire coat hanger to make a pointer. First you fing TDC. Bets way is to remove both plugs and get one cylinder to TDC with valves closed and make a positive stop to set TDC.

That means making a rod that stops the piston at 20-30 degrees before TDC. Here's some: https://duckduckgo.com/?t=ffab&q=Piston+positive+stop&ia=images&iax=images

I have a set of Vance and Hines set aluminum stops I bought decades ago, but I usually just hollow out a spark plug and put a bolt in it. Here's one I found on ebay but make sure that it's the same thread size as your spark plug. Plugs come in 10,12, and 14mm for bikes in 1/2" or 3/4 long threaded section. Yours will be 14mm by 3/4 inch most likely.

You slowly rotate the motor back to say 30mm BTDC (or 90 degrees) and screw in the adapter. Be gentle. The valves should both be closed so don't rotate it too far.

Slowly rotate the motor forwards and you will feel the piston contact the stop. Adjust the timing wheel and/or pointer to say 30 degrees. Just note what you set it at.

Now back the stop out and allow the motor to rotate forwards to about the say say 90 degrees or so ATDC.

Screw the stop back in and now rotate the motor gently backwards. Yes back towards TDC until the piston contacts the stop. Now you are the same distance down on the exhaust side as you were on the intake side.

Read the timing wheel and it will be quite different to the intake side. It might be 40 degrees or 20 or somewhere different. Just right down that number and adjust the wheel or pointer so that it's half way between the two numbers.

repeat and you will see the intake side will now show a similar number to what you just adjusted teh exhaust to. You may have to repeat that until both are the same.

What you now have is the same reading before and after TDC and the magic part is that when the pointer points to TDC that is exactly TDC.

Using a dial indicator or plunger is not accurate enough because of the latency at TDC.

Now hook up the timing light to its own power supply and clip the sensor around the HT lead (same side) and fire the bike up and see where it fires. You have to look straight at the wheel and pointer to avoid a parallax effect. Right down the timing either at idle or at full advance. then move the timing light clip to the other side and see where that fires. If both are identical, pour yourself a stiff drink and relax. If they are more than a degree or maybe 2 out, then the ring cam is an issue and has to be machined/tweaked to bring both back the same.

Write things down so that it's easy to repeat.

Is that all a PIA? Yes but they say the devil is in the details, but that's one reason my 500cc T100 was faster than most 650s back in teh day.. Attention to details (plus a 650 crank, slipper pistons, gas flowed head, race cams and pair of chopped monoblocs like yours. :)
 

pidjones

Over 1,000 Posts
I'll second the monoblock float bowl extension. My first bike was a Triumph TR6C 650 Trophy - twin cylinders just like a Bonny, but with a single monoblock carb. If you took the extension off (mine was billet machined with finsm I thought it was just for show) it would pull the bowl low (not dry, but to where it began to suck air) about the time you got it nearing wound out in 3rd (right when it felt great!). With the extension it would pull hard all the way. Lucky I didn't blow it but then it was chopped and I mainly cruised and commuted on it. Even if you can't find one it would take less than an hour to spin one out on a lathe.
 

AgentX

Over 1,000 Posts
Teazer, can't thank you enough for taking the time to write that out. Wealth of info I'm going to save offline for sure!


re: float bowl extensions, I've seen them around on the Net; I think Amal might actually be selling them themselves.

That said, on this bike, I think there's little chance of me running down the bowl...single leading-shoe on public roads with trials tires...just not gonna be pinning it like that. That's actually one of the reasons I considered a single-carb conversion; it's all low-and-mid range for me. Going much over 70-80 isn't really in the cards for me with this one, and if a Mikuni offers both ease of use and performance improvements in those areas, it might be a good idea. I like slinging the bike through marked 15-mph corners at 45, not blasting it flat-out on the highway straights.

That said, the chopped monoblocs are *very* cool and, apparently, quite rare now. I'm learning to live with the awkward access to adjustment screws and stuff, so all in all, gonna hang on to them and not start another science experiment (or wars over Britbike heresy). (Not that I'd ever get rid of them, even if I did mount a single carb of some sort!)

Maybe I'll get the bowl extension down the road once everything else is sorted, if it seems I might need one.

As for vintage pure-vanity items, I do have finned Dunstall rocker covers which the original owner installed in the 60s then removed because, well, "they were just vanity..." I might throw them on the next time I check valve lash, just for fun.
 
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AgentX

Over 1,000 Posts
IMG_20200411_184637671_HDR.jpg


Take 3 on the tach drive, after the last explosion. Swapped both gears from another unit which had busted threads on the body. Used Mr. Jefferson up front under epoxy and pure epoxy on bottom. Let's hope this keeps it together.
 

AgentX

Over 1,000 Posts
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.

IMG_20200413_155003134_HDR.jpg
 

AgentX

Over 1,000 Posts
WOOT SPEEDOMETER DRIVE WORKS! I took the ring gear from the guts of the Emgo unit, whose final gear wouldn't engage the speedo cable properly, and swapped it into the original Smiths drive. Not as nice and easy as it sounds, but the job is done and dusted.

The good news on my front brake cable is that the threaded stud, where the adjuster screws into the brake plate, isn't damaged like I thought it was. Turns out the adjuster on my new cable, which is the correct length (shorter free cable than my existing one) has a different, but very very similar thread. So I gotta run down the specs and get a new cable with the right adjuster. I may trim the old cable and solder a new end on, too, but I don't have the right cable end or any flux right now...probably easier to get the right cable pre-made.
 

AgentX

Over 1,000 Posts
Outside...sounds less like underwater than in the garage. Little snarlier on the new timing.











Was thinking about float bowl extension..would be cool in plastic to see the float level...
 

pidjones

Over 1,000 Posts
Not many clear plastics hold up to gasoline. So, tach drive works now? Maybe it just doesn't like old Tom.
 

AgentX

Over 1,000 Posts
I rebuilt the tach drive again...used very little grease this time, thinking that maybe I had overstuffed previous attempts and caused lots of pressure at high RPM.

Also, I suspected maybe the drive spade was butted hard against the camshaft nut when mounted...so I shimmed it slightly outboard using an additional thin paper gasket (an Amal jet block gasket actually) and thin shim washers under the mounting lugs. (Keeping the central circle located in the timing cover, obviously...)

If it holds like this, I will shave a mm off the drive spade next time I happen to be working on the timing cover, then remount without shims.

And yeah, poor Tom gets rejected by everyone these days for his hypocrisy, I guess.
 

AgentX

Over 1,000 Posts
I'm still having trouble getting those cylinders to play well together. This is my first twin; my Enfield's a single. But when the carbs are in perfect sync, the LH cyl doesn't want to idle like the RH. Stumbles and feels like it's idling too low on that side; you can hear it sort of come in and out of play as the bike idles. If I pull the RH wire the LH won't run the bike solo unless I give it throttle and/or raise the throttle stop. If I adjust the throttle stops and mix so the LH cyl idles well, the RH is hyperactive (or I have to set it significantly differently on the throttle stop...). RH will run the bike reasonably well on its own with the throttle stop much lower.

Carbs are clean and cables not hanging up, slides snap down sharply when the throttle is let free...gonna do a compression test now (again) to try and see if maybe there's a problem deeper inside. Early on, I think the LH was a few PSI down from the right but within 10% or so. Don't have a leak down tester but will see if there's any attachments I can use on my buddy's little compressor to try that, too.

I might try moving the RH carb to the LH cyl and see if that changes things, though it's complicated by the chopped setup where I would need to keep the LH carb in play to meter the fuel. Can't see any reason I shouldn't run the bike with no carb on the RH cylinder...is there?
 
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AgentX

Over 1,000 Posts
OK, compression on both cylinders (cold) is ~100PSI, LH is like 98 and RH is like 102. It's a Craftsman testing set, not something super-expensive; not sure how accurate in the absolute, but my intent is really just to see if there's any difference across the sides. I'll proceed with other things and once things are warm in the course of testing I'll check again on a hot engine.
 

pidjones

Over 1,000 Posts
OK, compression on both cylinders (cold) is ~100PSI, LH is like 98 and RH is like 102. It's a Craftsman testing set, not something super-expensive; not sure how accurate in the absolute, but my intent is really just to see if there's any difference across the sides. I'll proceed with other things and once things are warm in the course of testing I'll check again on a hot engine.
With throttle and choke wide open?
 

AgentX

Over 1,000 Posts
With throttle and choke wide open?
Yep! But...seems to be running pretty well this morning now. Air filters are off to check the slides, but the filters haven't seemed to make much of a difference. In any case, I'm getting each cyl to idle independently at just over 1k and together they're working fine and slides are perfectly in sync.

Time to ride it for a bit! I'll re-check idle mix for each side on return assuming no other issues enroute.

(Edit: Aright, pretty sure that whatever the issues may have been, right now, after carb mounting/remounting etc, I'm facing an air leak, probably in the RH cylinder. Nothing else could account for the newfound issue of RPM running sky-high with the throttle closed, yeah? It is not the cable hanging up...I can visually confirm the slides closed to their stops when RPMs are climbing. But I'm done fucking with it for today.)
 
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