Carb setup questions

J

jacobsdad

Member
I have a couple more beginner questions. Still trying to get my mind centered on the whole 1 cylinder hot rod thing!
We are brand new to racing. Going to get a start next summer. My sons kart we got him has a 5hp briggs. I don't know anything about the engine.
If we set it up to run on alcohol, what do I need to do? I know it will require more fuel. On these carbs, is there a jet I can change and where is it? I assume I will also have to enlarge the fuel passages too, but what passages and where are they?
Finally, when I put the blue restrictor plate in it makes sense to increase the fuel flow. Is it common to do this with different jets, or with the mixture screw?
I am not sure if we will run gas or alcohol yet. It will depend on track rules. What does everyone else prefer for alcohol fuel? Not sure where to buy any in my area yet, but we haven't really looked yet.
Thanks for the carb help!
 
Alcohol should be readily available (speed shops and at the track.)
Alcohol will make slightly more power and the big benefit is that it will allow your engine to run cooler (important on an air cooled engine.)

I'm assuming since you're in Nebraska, that you'll be running by IKF rules.
For alcohol jets for the IKF blue plate, start out with 60-61. Set the mixture screw at 1 1/2 turns out. Metering holes are located behind the jet. They should be drilled around .059" rear, and .026" front. You can also work on the short stem and lots of other things in these carbs that affect fuel signal and flow.
I would highly recommend getting the engine blueprinted by a reputable kart engine builder. (Either one in your area or send it out to have the work done professionally.)

There is so much work that can be done in these engines that a beginner is going to get frustrated with their lack of performance if they have sub par equipment. Good used engines are also readily available. I've got several fresh small plate engines right now with prices ranging from $550 to $950.

Give me a call at the shop if I can be of any further help to you.

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com

Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
I'm wondering what it is about four cycles that they run cooler with alcohol? Our two cycles didn't run any cooler, you would/could still stick the piston, (overheated) if you got it too lean. I wasn't using the EGT in those days, so I'm wondering; what happens to the exhaust gas temperature with Alky? The CHT doesn't tell you a whole lot about what's going on inside the combustion chamber.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
if you plan on building or doing a lot of the engine work yourself you may consider our book on building the Flat head 5hps. it has a complete chapter on the methanol carb setup as well as all aspects of building the engine. our ad is below.


lots' of folks to help you here with any question but our book will answer a vast majority of them for you


Jimmy

http://www.4cycle.com/jglenn/
 
I have already learned a lot just by reading and asking questions on here. I have a long list of phone numbers of people who have offered help too! We won't make any drastic changes until closer to spring, but I want to use this time to gain all of the knowledge I can.
Al, I do know that the engine will actually run cooler on alcohol but am not certain exactly why. When I was in college for automotive tech back in 1980something we had an alternate fuel class. We dumped a cup of gas on the shop floor and dumped a cup of alcohol on the shop floor. The alcohol burned faster but cooler. When it was all burned off the floor where the gas fire was burning was hot and had a greasy film. The floor under where the alcohol was burning was cool to the touch and had no residue. Of course the instructor went into the reasons why it burns cooler and cleaner but gives better performance, but I was not paying attention. Or I have forgotten over the years, not sure which. In our stock cars and when I was drag racing we found that burning alcohol did keep the engine running cooler too. I know a V8 engine is a lot different than a 1 cylinder air cooled engine, but the end result in temperature should be about the same. I never ran demolition derby but a bunch of my friends did. They ran alcohol too because they said their cars ran cooler.
For now we are going to be stubborn and try to learn what we can about these small engines, then build our own. I asked my son if he wanted to buy a race ready engine, or if he wanted to build what we have. He said he wanted to build what we have. I told him that it might mean he loses a lot of races while we learn, he said "dad, I don't care about winning as long as we can work on it together". He said we will figure it out together. Besides that, I am stubborn. I don't like to buy my power, I would rather gather all information I can and build my own.
Thanks for the information on the carb jets! I will add this to our "notebook of knowledge".
 
If you plan on doing it yourself by all means invest in Jimmy's book. I guarantee it will pay for itself in money saved.
 
Thanks! So far I have 3 books that have been recommended to me on here. 2 on tires and this one. They are on my Christmas list!
 
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