cold engine blues

S

steven wardlaw

Joined
May 22, 2008
Messages
83
My 71 commando has always ran great even after installing single mikuni. I have had to run on choke for the first few miles until bike warms up, but never a problem. This morning was my first day to try it on a cold ride. It ran fine until I came to the first stop. Then it died. Cranked back up easy, (on choke) but again died when I tried to stop. I had to ride the rest of the way on choke. Please help!
 
steven wardlaw said:
This morning was my first day to try it on a cold ride. It ran fine until I came to the first stop. Then it died. Cranked back up easy, (on choke) but again died when I tried to stop. I had to ride the rest of the way on choke.
Click to expand...


I think the Mikuni single carb conversions can suffer from carb icing in cold weather? Having to ride with the choke on would be a symptom of that. You could try using different brands of fuel?
 
I have had the same sort of problem, mine was solved by turning on both fuel taps it turned out that the normal running tap had a restriction the gland type seal had moved and was causing a partial blockage. The mikuni on choke demands quite a lot of fuel, just try with both taps on to prove if it makes no difference then its something else.....if you have a restriction remove tank lay it on the opposite side to the obstructed tap turn tap to the open position and use an appropriate size drill (by hand with finger) to clear.Good luck

:) :)
 
The fuel supply is a good place to look also float height. But do not over look spark. We have a bike here that has a new Tri-Spark ing. with a single Mikuni fitted. With a Boyer it always needed a choke start now it does not require a choke at all. The the idle jet needed to be leaned a bit to boot. As with all "things" it's rarity when it's "just one thing"
 
I'd wonder where you are and just how cold it is. You can have carb icing if cold enough, but if it start right back and runs on the enrichening vlave it probably is not iced.
When the weather is cold enough the engine requires a richer mixture, this is easy to compensate for with Amals by just adding a bit of choke.
With Mikunis some of them have the enrichening valve as an either on or off device, so you might have a bit more problem with minor compensation.
If you run it long engough can you reach normal operating temperature?
Obviously bikes designed to run in cold weather like old BMWs can actually be fitted with warming devices for the cold.
I'd think if your bike is running in weather cold enough to affect your carbs it's time to go in by the fire anyway.
 
That why i wondered if he could recha regular operating temp. If it still won't idle there it might be gummed up from sitting.
 
cold idling blues

Hey sounds like what my bikes doing now that i installed new carbs. Use to close air valves start bike let it run a little then open air valves all the way .Now its start air valves closed let warm up try to open air valves and she starts to blubber runs strong closed but really haven't really got her good and warmed up temp outside 30's. Had to adjust float on right carb to low wouldn't flood when tickled.but i think i raised to much now right carb a little wet around air filter . Only thing different was needle in middle groove raised one notch. M.c.
 
Back in the 70's I rode all year round. As long as the roads were clear of snow I'd ride. I remember riding with 2' snow banks on side of the road. I don't recall ever having to adjust my amals for the minus below weather. I'd start it up and idle it for a few minutes before popping it into gear. The funniest thing was how the 6"-8" flat spot on your tt 100's would freeze when the bike sat for an hour or so. The bike would bump-bump-bump along for a few miles till the tire thawed out.(we thought this was the funniest thing)

It would have been nice to have heated handle bar grips because I sure wore out a lot of gloves from burning them on the heads from trying to keep my fingers from getting frost bite. We used to have to ride with our left hand on the throttle so we could thaw the right hand, always alternating.

Awe, the good old days...
 
I don't recall riding those suckers in the snow that fondly. Traffic backed up behind you on the Maine turnpike while you slowly cruised on the side of the raod.
The real job was getting it started if you had single weight oil.
Summer would come calling just enough to fool you into getting stuck in a snowstorm or finding it had snapped below freezing when you came out of the pub. Burrrrr!
 
Cookie said:
I don't recall riding those suckers in the snow that fondly.
Click to expand...

Haw! yeah, when I wrote "awe, the good old days" I was thinking of the stamina we had when we were young (I won't go into the brains department).

You'll never catch me riding in those conditions again! (I hope)
 
When I moved to SF the Commando was my only transport. Easy to park about anywhere and my girl friend and I thought the rain was nothing compared to the frozen east. I wonder why she left me...?
 
Well everyone has came to my rescue. Thanks, but the problem was finally solved on the ride home today. Bike started on first kick and purred as usual. I thought that everything was great until I stopped in front of about 25 other cars getting off work. Dead again! This happened almost half my ride home until I finally stopped to try and fix it. Everthing looked good. As I was turning the bike around with it running I touched the brake, and that turned out to be my problem. If you touch either front or rear brake it dies. Okay, now we can look for the lucas gremlin. Thanks everybody for your help.
 
Steven, If people were more honest they would tell you how many hours they have spent working on a perfectly good carb. I will tell you that getting a real good electrical system will find you some of the cheapest HP you will ever buy. How many carb booklets start with the sentence "Be sure the machine is timed and the plugs are in good working order."
 
I have not tried to fix the problem yet, but I think the brake light wire is touching somewhere. The one real possitive note to all this is I've learned how to truely kick start this bike. I usually put it on the center stand and stand beside it. That's hard to do in city traffic. I must of started this thing twenty times yesterday. It's not that hard when all the horns are blowing.
 
the best thing to do in that situation is tell the guy or guyess that you will blow the horn if they will start the bike for you.... :twisted:
 
Great,

That sounds like a really easy fix. It is probably a chaffed wire, look where it flexes on the brake pedal first.
 

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