Slow to warm up

[jsandidge]

I haven't seen this particular question asked. My bike is slow to warm up before I can shut off the "choke". Probably a full 3-4 minutes or so. Once warm, it will run fine. It idles smooth, and has good throttle response. This is in my garage on an auxillary tank, as I can't ride until I clean and seal my rusty tank.

Carbs have had the full strip and dip for 24 hours, although I did not poke a wire or anything through any of the ports. Carb cleaner and compressed air was blown through. I did poke through the holes in all the jets. All jets are stock as verified with the factory manual. All new o-rings from Robert Barr. New boots and o-rings, stock airbox sealed with new weather stripping. Exhaust is stock with no leaks. Carbs have been vacuum synched and mixture screws adjusted. I still get a slight popping if I rev up to about 6k which isn't as bad with the mixture screws turned out about 3-3/4 turns which I know is about the upper limit.

Compression is only reading 90-95 across all 4. The bike had been sitting for 14 years before I got it. It has a little over 46k on the clock.

All electrical connections have been replaced or cleaned and a new SH775 has been installed. I have not done the coil relay mod, but plan to. New plugs and boots have been installed, with the wire ends trimmed back.

Could this be due to low compression, or are my pilot circuits still a little clogged? Should I just ride and hope the compression comes up? The warm-up time does not seem normal.

 

[cowboyup3371]

Have you adjusted your valves yet?

 

[jsandidge]

valves adjusted

valves adjusted

Have you adjusted your valves yet?

Forgot to mention that. Yes, I did adjust the valves. Had to replace a few shims and swap around a couple others. All in spec now as measured by the official factory manual method.

Edit: Also forgot to mention fuel heights were all set using an adapter and clear hose from the bowl drains.

 

[robertbarr]

Probably every carbureted UJM ever made is slow to warm up, even brand new. My trusty Honda Nighthawk can idle indefinitely from cold start, but it isn't fully ready & awake until I've ridden it five or six blocks.

That said -- after sitting that long, I think you have the right suggestion, which is to put it on the road and give it a thousand miles or so. It sounds like you have all the bases covered.

 

[tkent02]

Probably every carbureted UJM ever made is slow to warm up, even brand new.

Not the ones that are jetted too rich. But several minutes is too long unless it's sub-freezing weather.

Don't worry about shutting off the choke, how long before you can ride it gently? Start it, put on a helmet and gloves, ride down the street, by about the second block you can shut the choke off. Might have to play the throttle a bit to get it to go at first.

If you can't give it enough throttle to ride gently down the street after a minute, it's too lean.