Ethenol blend gas source of cooling problems? By billg (Read 598 times)

[billg]

I got another carb for my Lance Duke 250.  The idle mixture screw had frozen in my old one.  The new carb (from China) didn't even have a brand name or model number on the body, but it works fine except that it runs lean according to the plug.

I took the needle up one slot, but still not enough.  Only one slot left which will be taken up today.  I do like that it will start and idle cold almost immediately, unlike than the old carb.  Never the less, it seems to run hotter.

I checked the main jet which is the same size as the old carb, a #110.  I think I'm gonna need a bigger jet.  Are larger jet numbers bigger or smaller?

It occurred to me that overheating problems I'm having and that I am reading about here may be due to a change in gasoline to include some ethanol, which mixture if I remember correctly, burns hotter.  I think the mixture here in California is 10% ethanol, but don't quote me on that.  It would also explain my idle mixture screw freezing.

If ethenol is the problem there may be a run on bigger jets before this is all over.

So from a #110 jet, which is a larger jet, a #108 or a #115?

[scooter2]

Mar 29, 2015 19:21:20 GMT -6 billg said:

I got another carb for my Lance Duke 250.  The idle mixture screw had frozen in my old one.  The new carb (from China) didn't even have a brand name or model number on the body, but it works fine except that it runs lean according to the plug.

I took the needle up one slot, but still not enough.  Only one slot left which will be taken up today.  I do like that it will start and idle cold almost immediately, unlike than the old carb.  Never the less, it seems to run hotter.

I checked the main jet which is the same size as the old carb, a #110.  I think I'm gonna need a bigger jet.  Are larger jet numbers bigger or smaller?

It occurred to me that overheating problems I'm having and that I am reading about here may be due to a change in gasoline to include some ethanol, which mixture if I remember correctly, burns hotter.  I think the mixture here in California is 10% ethanol, but don't quote me on that.  It would also explain my idle mixture screw freezing.

If ethenol is the problem there may be a run on bigger jets before this is all over.

So from a #110 jet, which is a larger jet, a #108 or a #115?

115. a 115 is 1.15mm

[Alleyoop]

Yes put a 115 main jet in it, another 250 guy just yesterday got a new carb and it had problems because the main jet was a 110 he swapped the jets from the old carb which was a 116 and he is a happy camper.
Alleyoop

scooterdoc.proboards.com/thread/11575/installed-carb-scoot-stalls-when?page=2

[gooter]

The idle mixture screw is royal pain to reach on the Dukes....I am able to reach it with the special "L" shaped tool on the left side of the scooter with the plastics off...it is doable.

You have to reach between the airbox and the frame and position a small flashlight on to the screw...all you can see is the glare of the screw and turn it as required. It's not easy but I was able to set my mixture perfectly while hearing the rise and fall of the RPM's as I turned the handle of the tool ..the Air/fuel mixture is set right by the color on the spark plug...and the scooter runs exceptionally.

Not sure about the ethanol fuel....seems like it can be a contributing factor to my Dukes heat "running away" if it is not controlled by my fan set up...as noted in the other Duke 250 thread.

[billg]

scooter2,Alleyoop,gooter

Appreciate the feedback, all.  Got a 118 jet from my local dealer.  Thanks Alleyoop.  That's all they had.  It's going in tomorrow.  A full selection of jets can be had at scrappydogscooters.com under 'CF250 172mm Helix parts'.

I ordered the fan gooter recommended.  Figure I'll just replace the puny stock fan and keep the same temp switch and see how that works out.  I've had no trouble with the temp switch coming on (at about 80% hot) and cooling the engine back down in city driving.  My problem has been getting it to cool down on the freeway at 70.  I'm looking to cut some louvers in the bottom panel of the Duke to get some air in there.  It could be that is the (capacity) problem, so will do that before replacing the fan.

What are we going to do if they go to more ethanol than 10%?

Cheers!

[jct842]

I doubt if ethanol is directly causing cooling problems. It has less energy than gas. It does require using more fuel to do the job. Hence the needing bigger jets and making an engine run lean with jets designed for gas. With the right jet it should run slightly cooler than gas.

Used to be a class of race cars called "midgets", they burned straight alcohol and I don't ever remember them ever having cooling problems, they just used huge amounts of alcohol and must have got like 1 or 2 miles on a gallon of that stuff.

[richardv]

Ethanol does cause cooling problems. It makes an engine run too cool and gasoline has to be added to get an engine to start and warm up. I got this information from my grandfathers and a neighbor that made his own from '90 to '05 as used it in his tractors.

[billg]

I got the #118 jet in and encountered a problem. The engine would start with no throttle and then bog down it any throttle was added. The CV slide was not lifting. I put my finger in and lifted the slide (manual calls it a vacuum piston) manually and it worked. I thought the diaphragm might be damaged, so I switched in the one from my old carb. Same thing. I thought maybe the bigger jet was the problem, so I put the #110 back. Same thing. Finally, I cut about 2 turns off the diaphragm return spring and WOW. Not only does it work right but it develops a lot more horsepower. Does anyone have any experience with this? Am I correcting for a clogged port or a vacuum leak or are the stock slide return springs actually to long?

[cyborg]

I've had springs be too strong and did the very same mod you just did,,, with perfect results and with no long term adverse affects