Topic: K7 running better when cold...why?

[anotherCB]

I have played with my carb settings a bit, put in 120 main jets and pod filters and the bike definitely runs better than it did with the 110 jets which I believe are original for a PD41A carb. I still have a little bit of a hesitation though when I fully open the throttle at say 50mph in the highest gear. This does not seem to be the case when the bike is colder. The warmer it gets the more hesitation there is. Does that indicate anything in regards to the carb settings (too rich, too lean?). Thanks.

[Leanier]

I'm pretty sure that would indicate to rich.  as the engine warms so does the air I'd think, warmer air means less dense, which means less air, thus needing less fuel.

[GammaFlat]

Your condensors may be failing when warmed up.

[Skunk Stripe]

Here is a test. What happens when you pull the choke when the engine is warm and you twist the throttle?
What do your plugs look like after running?

[anotherCB]

Will try to pull the choke when I get to it tonight and let y'all know. Plugs look good to me.

[anotherCB]

Just realized I had overlooked the comment about the condensers, how can I test them? Thanks.

[TwoTired]

I still have a little bit of a hesitation though when I fully open the throttle at say 50mph in the highest gear.

After the hesitation, describe recovery, does it burble/sputter back into power, or come back cleanly like "switched back on"?

Do check/describe your spark plug deposits, and if they are the same for all cylinders.

[GammaFlat]

Just realized I had overlooked the comment about the condensers, how can I test them? Thanks.

Replacement is probably easiest.  If they're a couple years old or older, it's a good idea anyway. 

[anotherCB]

@TwoTired: Definitely it comes back like "switched back on" and not like "burbling/sputtering back into power" especially when I roll the throttle back a little bit (I have heard before this means "too lean"). Will get a better read on the plugs soon. Thanks.

[TwoTired]

@TwoTired: Definitely it comes back like "switched back on" and not like "burbling/sputtering back into power" especially when I roll the throttle back a little bit (I have heard before this means "too lean"). Will get a better read on the plugs soon. Thanks.

Yes, too lean.  Which is odd for carbs with accelerator pumps.  You may wish to investigate that pump and the circuit.   I had one that didn't work.  Rebuilt it, so it did, but it wasn't working well enough and behaved rather like you describe.  Re-cleaned the two check valves to ensure proper seal, and found the "mickey mouse ears" on the diaphragm were swelled and partially blocking the passage they sealed.  I opened those and then got a MUCH stronger shot of fuel overall, and a better partial shot with smaller throttle twists than before, ... all stumble gone. 

This was a Cb750F with stock exhaust and K&N air filter in the stock air box. 

Cheers,

[SKTP]

I still have a little bit of a hesitation though when I fully open the throttle at say 50mph in the highest gear.

I have a k8. If I was at fully open throttle in the highest gear I would be doing 110-115mph...if you are only hitting 50 something is very wrong.

[anotherCB]

@SKTP: No, I didn't mean 50 was max speed, I hit 120mph relatively easy, however I cannot "yank" the throttle open at 50mph in 5th gear. For max acceleration I have to open and close back a bit for a few times until I reach higher rpm. Doing this, I quickly get from 50 to 110+ :-)

Good idea with the accelerator pump. Allthough I rebuilt the carbs and everything looked good to me. It "squirts" a good amount of gas in all 4 carbs which I can see when the filters are off.

[Skunk Stripe]

You got pods huh? What brand? The cheap ones are very hard to tune right. The k&n work better but 120s might not be large enough. Although, at 50 in 5th, you are also not in the powerband at all. Ease it to 75 and see if things are better, you will at least be in the start of your main powerband then, and running a bit more in the mains and if you still have the issue, good chance your mains are too small. You can kinda test this by partially closing the choke a bit to see if it will help.

[anotherCB]

Yes, got the cheap pods. I was hoping to do some testing tonight but that won't work, will do it in the next days and let you know what i find. Thanks again for everybody's input!

[anotherCB]

Ok, no test run in the next days....found a leak under my brake caliper last night and after I took it apart realized that I need to rebuild it. I am in the marke now for a piston and seal :-(