A late 72 journey out of hibernation (2020)

jbruney said:
Sounds like mine was acting before it went into orbit. It was the drive though.
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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.
 
Just curious, how did you adjust the valves without determining whether the bike has a combat cam? The settings are different.
 
rvich said:
Just curious, how did you adjust the valves without determining whether the bike has a combat cam? The settings are different.
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Out of caution I used the wider combat specs, shrug. Still haven't heard anyone's opinion on a (simple, HAH) way to determine which cam it has.. I'm all ears....
 
I agree that wider is better if in doubt. I found a C on my head so I bought a cheap dial indicator at Harbor Freight and rigged it up to measure the valve lift on the inlet side. The difference is enough that even with some error you will get a pretty good idea of what's in there.
 
rvich said:
I agree that wider is better if in doubt. I found a C on my head so I bought a cheap dial indicator at Harbor Freight and rigged it up to measure the valve lift on the inlet side. The difference is enough that even with some error you will get a pretty good idea of what's in there.
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Do you have the numbers off hand? Just going down to remove the tank to do the exhaust valve cover seals and new throttle cables, I have dial indicators. Where is the C located? Please and thanks!
 
If you have dial gauges just measure the valve drop. A 2S has more lift on the inlet than the exhaust, so that’s really all you need to check for.

Head marking should look like this:

A late 72 journey out of hibernation (2020)
 
Sadly the C is under the head steady so you have to take it off to look.

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.

The numbers are from Section A, page 22 in the manual.

You will be glad you checked.
 
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It is unclear to me whether the RH5 and RH6 heads were stamped above the right exhaust valve. But you can look there for numbers as well.
 
I guess another way of testing to see if it’s a Combat is to ride it... whack the throttle open and see if it tries to pull your arms out of their sockets above 4500rpm !
 
gggGary said:
A week into ownership; I got the smmotorco primary cover seal, so redid the primary. Found the main culprit was no grommet on the alternator wire! A glob of silicon was just hanging from the wire.... Now with a grommet installed and some wire rerouting so it's not rubbing on the cradle. Extensive clean up of flanges and the seal groove, found the new seal was about an inch short, just used a bit of the old to close the gap :confused: put the seam up top bolted it all back up and took off for a 200 mile "test ride" . Much better! Think the primary is tight now. Need to stop some exhaust valve cover drool and she should be good to go til the tranny gets gone through. Glorious day for a ride, sunny dry 60's, back roads Wisconsin. Not done with carburation yet, higher throttle is great, kinda lumpy surge-y at lower speeds, will install the new throttle cables and have another go at synching. After one ride working perfectly, the speedo wandered off into Jittersville, oh well, one step forward, one back. I have now put more miles on the bike in the last week than it had gone in the last 4 years. Will be calling around monday finding a way to get a reduced bore front MC as soon as possible! With lots of deer encounters waiting patiently for the bike to slow down is just not an option. Got cut off in a small town yesterday, truck driver looked right at me and pulled out in my path anyways. I was cursing that pitiful front brake again! About 3 miles later an SUV had rear ended a minivan, if they can't see a minivan....
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Truck drivers are usually the best ones.
 
Amals have 190 mains, stock airbox, peashooters in good condition, of unknown parentage but not real loud. Manual sez 210 depending on mute or not. Plugs look good to me. Getting about 45mpg on premium @ 60-65 MPH ie 4100 RPM comments?
 
i had to drop down to 190 mains on my 72 combat with stock air box and peashooters with no mutes (viking mufflers) .
 
It's been a bit, Lots been done, lots yet to do and a question for the brain trust.
So dropped the dime and got a pair of Amal Premiers.
Had them set to 750 combat specs.
220 mains
3.0 slides
106 needle jets.
Even changed out the T spray tubes for the straight ones.....
Tank cleaned with electrolysis.
New 12 volt battery and a digital voltmeter. It's showing charging good.
Okay to the chase fired it up last night runs great the mid range blubbering is gone. Runs all regimens good or better Except idle is very inconsistent, with a long period oscillation from say 500 rpm up to 2000 and back down, again this is over 10 seconds or more. Put on the gauges I'm synched,both cables and stops, adjusted mix screws from 1 turn to 1 1/2 turns out doesn't change the oscillation. I have not checked the float levels, just left them as delivered. I'm thinking it's not carbs but???
Have not done much with ignition still points, mechanical advance. I have a Wassell/Vape ignition with electronic advance sitting here now, and am leaning towards just putting it in. And seeing if that fixes it.
Valves set and checked.
Compression is not stellar 135L 150R left intake valve shows a bit of leakage.
It's an easy (too easy? Ha hah) one kick start, cold or hot.
Any other ideas of what's going on, what I should be looking for?
 
Just to qualify....I don't have experience w/ premiers. But read a thread on here very recently regarding the float and trouble with the factory setting... might be worth looking in to. P.S. Nice looking Combat you lucky sod :) ...very well sorted and set up looking stablemate you have there in the XS 650 too, if I do say so myself.Cj
 
First thing to check is the slide synchronisation / cable adjustment. Next thing to check is the pilot jets. They may have been supplied with #17s but many find they need the richer #19s. They are identified by ‘rings’:

1 Ring - 622/502-15 (Equivalent to 20 Pilot Jet in pre-Premier carbs.)
2 Rings - 622/502-17 (Equivalent to 25 Pilot Jet in pre-Premier carbs.)
3 Rings - 622/502-19 (Equivalent to 30 Pilot Jet in pre-Premier carbs.)
4 Rings - 622/502-21 (Equivalent to 35 Pilot Jet in pre-Premier carbs.)
5 Rings - 622/502-23 (Equivalent to 40 Pilot Jet in pre-Premier carbs.)

Do some searching on here. Many, myself included, have chased mystery carb issues only to discover it was down to this.

There are many other things it can be, but always best to start with the common and / or simple possibilities.
 
Ok #1 checked the pilots; 3 ring #19 in place and blown clear just to be sure.
All other parts were checked to confirm correct. Next up checking float levels.
Thanks for the help n suggestions so far.
 
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Raised the fuel level "a bit" it was pretty low, reinstalled confirmed no air leaks with carb cleaner sprayed about at idle.
Really bout the same, runs out great, accel steady running all rpms, decel all good, but still idles at about 2K if I pull it down with a slight release of clutch it drops to 500 RPM and stays there. :oops:
 
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