Topic: What's the fix for crappy running when the engine is hot?

[grumpy]

My K3 gets all sluggish and put-put-y while rolling around town when the engine is hot.
Really noticeable when accelerating off a stop light.
Air temp doesn't really matter - just engine temp (but obviously hot days compound the issue).

So what's the fix?

(plug reads are OK)




 

[bjbuchanan]

could be a lot of stuff but leanness comes to mind. Needle clip position

It is slowly getting hot from running lean

[bollingball]

Hot is so relative how about some temps. What do you call hot? When it is over 92f it starts to get hot to me. Not the bike but me. Now during the summer when it gets over 80f any air cooled engine with no fan will start running different when at a light or stop & go traffic in town avoid this if you can and like bj said running lean is a no no too.

Ken

[grumpy]

any air cooled engine with no fan will start running different when at a light or stop & go traffic in town

right - that's what I'm talking about.

is there any secret 70's fix/tweak for it (other than avoid it)?

[bjbuchanan]

Nope

As long as the bike is in good tune there isn't much to do except maybe ride different routes or something. My aircooled corvair was the same deal. It ran great but you could tell in bad traffic or really hot days it wasn't particularly happy

[grumpy]

bummer.

oh well.


WAIT!!
How about a water injection system. It could mist into the top half of the air box right in front of the stacks! Better cooling AND more top end power!
YEAH!

meh, maybe not.

[lucky]

You will need to give us more information.
What kind of exhaust and what kind if intake system?
What year is it?

Are all of the jets stock?
Is the slide needle in the stock position?

[flybox1]

bummer.

oh well.

WAIT!!
How about a water injection system. It could mist into the top half of the air box right in front of the stacks! Better cooling AND more top end power!
YEAH!

yup! pee on your engine at stoplights.... 

[bollingball]

These bikes when in there stock configuration have been dealing with this for decades. So Lucky might have a point how is your bike setup. Even when stock they can only sit at a light in the summer but so long. The older Harleys were even worse.
Ken

[Bankerdanny]

Heat related vacuum leak at the intake? Have you tried getting it up to running temps then tightening the clamps?

[grumpy]

nah, pretty sure it's just the air-cooled-engine-at a-stoplight syndrome.
I was just hoping there was a cure.
Just for grins I went to 7/8 on the air screws (from 1) and it got a bit more put-y. So I'm assuming it's not lean.

I do kinda like the water injection idea though. IF it worked for WWII fighter planes then it should work for us, right? 

[bjbuchanan]

It works well but you gotta have the tank around and full. A windshield washer pump from the rear of a minivan is the redneck homebrew way. Injected windshield washer fluid into the intake manifold rubber would be kinda slick

[scottly]

An oil cooler might help...

[grumpy]

It works well but you gotta have the tank around and full. A windshield washer pump from the rear of a minivan is the redneck homebrew way. Injected windshield washer fluid into the intake manifold rubber would be kinda slick

OHHHHHHHHHHHHHHHH  man... that's so flippin brilliant.

this isn't gonna end well, I just know it...

[Duanob]

I just think its the nature of carberated vehicles. i notice it on cars, boats, motorcycles, etc. It's been a while since I owned a carbed car but I remember the best it would run is first thing in the cool mornings. Same with my boats they all run better first thing, then after an hour ot two coming into the dock they jjust don't run as smooth when the air to the carb is too warm.

I don't notice that at all on an FI vehicle.

Just my $0.02

[bjbuchanan]

FI has the sensors and tuning maps that compensate with more/less fuel and timing at different rpms's to adjust for all those issues. That is why they are employed in their endless feedback loops. Carbs just cant do everything for every condition if they could we probably wouldn't have went to EFI


The methanol injection is pretty cool. I was about to nut up and do it on my corvair when someone gave me an offer I couldn't refuse. It is really easy to set up as it is nothing like nitrous oxide or a power adder. The methanol latent heat of vaporization cools the charge and gives the engine some nice cool air in hot weather. It bleeds the heat off in a way that doesn't need timing adjustment or changes in fuel delivery but is fun to play with

[2wheels]

Maybe your valve adjustment is too tight.