88 Honda Shadow VT600C long warmup time

I've got a 88 Honda shadow. Seems that the first run of the season it
always takes a real long time for the bike to warm up to the point
where I can crack the throttle.

I started it up yesteray for the first time this season and it had to
warm up for about 30 minutes before I could ride it. Before its warmed
up it will stall if you try to give it gas.

For as long as I have owned the bike the first warm up has always taken
a long time but seems to be getting worse as the years go by.

Any ideas what might be going on? I only ride the bike a few times a
year. Its only got about 4,000 miles on it.

Any hints of what to check are greatly appreciated.

Thanks in advance.

 

Thanks for the reply.

I tried the B12 with no luck.

How do I go about filling the floats with carb cleaner. Is there
anyway to do this without taking the carbs out? I have the tank off
and easy access to the fuel line.

Thanks again!