KZ650-B3 cold cylinder at startup

Hi guys long time no post but hey bikes been good,
Anyway as title when I start the bike after a few days of standing cylinder 3 doesn’t seem to warm up, header is cold, plugs dry so you’d think no fuel, however after a while she warms the cylinder runs as it should and the bike doesn’t miss a beat? I pulled the carbs last year and fitted larger pilot jets and checked and cleaned the carbs as you would expect.
Don’t think it’s electrical and it’s so weird it does it after being stood for even a short period. I checked the fuel bowl and there was petrol present ?
Anyone had a similar fault ?

MauserXR wrote:

Hi guys long time no post but hey bikes been good,
Anyway as title when I start the bike after a few days of standing cylinder 3 doesn’t seem to warm up, header is cold, plugs dry so you’d think no fuel, however after a while she warms the cylinder runs as it should and the bike doesn’t miss a beat? I pulled the carbs last year and fitted larger pilot jets and checked and cleaned the carbs as you would expect.
Don’t think it’s electrical and it’s so weird it does it after being stood for even a short period. I checked the fuel bowl and there was petrol present ?
Anyone had a similar fault ?
 

Whenever I have engine run issues I always go back to check basics : compression/spark/fuel/timing
Yes I have dealt with the one cold cylinder issue.

You confirmed that there is fuel in the float bowl on that cylinder, good start. If no fuel on spark plug then nothing is drawing fuel into the cylinder.
What is the compression on that cylinder? Did you check the valve lash?

Being your own mechanic is like being a detective.
 

Injected wrote:

MauserXR wrote:

Hi guys long time no post but hey bikes been good,
Anyway as title when I start the bike after a few days of standing cylinder 3 doesn’t seem to warm up, header is cold, plugs dry so you’d think no fuel, however after a while she warms the cylinder runs as it should and the bike doesn’t miss a beat? I pulled the carbs last year and fitted larger pilot jets and checked and cleaned the carbs as you would expect.
Don’t think it’s electrical and it’s so weird it does it after being stood for even a short period. I checked the fuel bowl and there was petrol present ?
Anyone had a similar fault ?

 

Whenever I have engine run issues I always go back to check basics : compression/spark/fuel/timing
Yes I have dealt with the one cold cylinder issue.

You confirmed that there is fuel in the float bowl on that cylinder, good start. If no fuel on spark plug then nothing is drawing fuel into the cylinder.
What is the compression on that cylinder? Did you check the valve lash?

Being your own mechanic is like being a detective.

 

If it doesn't run when cold, but does when hot, that suggests that the choke passages in the carb and float bowl may be plugged. 

BTW, the photos are for CV carbs, but the idea is the same.  When spraying to check the carb body passage, put the small straw from the carb spray in the small hole in the bottom of the choke plunger passage.

Many thanks the choke is just an enricher but I like the idea of this being at fault all the same 👍I guess it’ll mean pulling the carbs out again as not really possible to work on them in situ.
The rubbers are not to bad to work with but as we all know the airbox just doesn’t go back far enough lol. Might have a look when the tanks running low on fuel.


 

Was hoping to report back saying the enricher tube was blocked but it wasn't lol. Everything checked out OK....I started her and all 4 warmed up which either means there was a partial blockage which I cleared out whilst testing or it was a lucky start? time will tell.