New engine (upgrade in progress)

[Screendoor]

Could I possibly damage the engine running the choke at this level? Or is it more of a performance thing.

 

[anderkart]

Probably no immediate damage, but possibly long term.

All your doing with the choke on is cheating to get the air/fuel mixture closer to being correct.

If your intake gasket is leaking your probably sucking dirt into your engine.

If you have an intake leak and/or your main jet is too small you'd just have extremely lean air/fuel mixture that would increase the temp inside your combustion chamber and cause more wear on the whole engine.

 

[Screendoor]

Guess I will try to pull that jet

 

[jareeB]

Guess I will try to pull that jet

on oldminibikes.com they tell you to put a .90 or .92 main jet in, if you didnt do that then thats your problem

 

[Screendoor]

How much will a larger jet improve performance?

 

[anderkart]

How much will a larger jet improve performance?

You might not notice any difference in performance, but your main jet probably is a little bit too small for your engines mods, but most likely only while riding at high engine speeds. Some engines actually make more power when they're jetted a little too lean...

My Buddy's 6.5 clone engine kart has the exact same mods as yours, his runs perfect and makes very good power with the stock main jet and the choke fully off! Although his spark plug readings do confirm he's jetted a little too lean.

I think your major problem resulting in your engine having more power with the choke on is either:

Your carb mounting nuts are just loose,
Or your carb mounting gasket has been mistakenly installed backwards where it cant make a seal,
or your valve lash needs to be re-adjusted,
or your carburetor needs to be cleaned/adjusted,
or your choke is somehow malfunctioning,
or you do just need a larger sized main jet.
Or a combination of 1 or more of those.

Once you check a few things you could install a new spark plug (NGK BPR6 gapped at 0.35 is a good choice) and then just use the choke only as necessary to start/warm up the engine. Then go out and ride the kart real fast for a bit so you could take an accurate spark plug reading and learn if you really need to re-jet the carb or not.

But if you dont want to go to all the hassle of doing things correctly, and just wanna guess at a properly sized main jet, an 80 through 92 size would get you somewhere in the ball park. Might try an 85 first.
They're available here: http://www.nr-racing.com/stockparts.htm

You haven't even responded so some of my advice about this choke issue, that's cool but I'm starting to feel like I'm talking to a brick wall here... I enjoy helping and think your a good guy and have enough mechanical aptitude to understand things, but for now I'm starting to think your either going to need to pay somebody like that race kart shop to get your engine all dialed in correctly, or spend some serious time researching at a kartracer web site to learn all about the little details that can affect your engine. If you would have left your engine all stock you probably wouldnt be having these problems.

If you registered/signed up at this forum: http://karting.4cycle.com/forumdisplay.php?f=120 You could use their search window and enter search terms like "clone main jet" or any other subject as long as you begin with the term "clone". You'd get tons of free info from guys that build these race engines everyday for a living, and also from guys that race these 6.5 clone engines at a kart track every weekend.

Those dudes know way more than me or probably anyone else here on DIY. You cant believe every post over there just like here, but if you research long enough you'll get to where you fully understand your engine and be able to tell who's giving good advice or not.

 

[Screendoor]

Sorry I havent got on in a few days I have been busy doing military type stuff!

I really have not been able to work on the kart but might try to 2morrow.

 

[Screendoor]

Today I flipped the PBR kart. I landed on my feet and prevented the kart from rolling all the way over. I would say that it was pure luck along with my beyond cat like reflexes

 

[Screendoor]

Sorry I have not been on in a while. Uncle Sam has me super busy and he doesn't want to pay me for my time. I have noticed that once i tightened the bolts on the carb it did not help. So with that being said It could be a problem with the gasket. I will pull it one night this week.

 

[anderkart]

Flipped it, dang it sounds like your riding that thang like you stole it!

Yeah your carb gasket could be defective or even just mistakenly installed upside down.

 

[Screendoor]

man I was driving in a parking lot and took a corner too fast and started to slide, the tires caught traction and the kart started to roll.

 

[anderkart]

Yeah I'll bet that was a rush.

If you ever get a modern style sprint kart it'll have super wide axle/rear tires and you'll find its nearly impossible to roll over like that.

If you ever feel your kart (or car) starting to roll again you can usualy save it by quickly turning the other direction.

 

[Screendoor]

It happened so fast there was no time to react.

 

[anderkart]

Well now that you know that can happen, use those "beyond cat like reflexes' of yours and just always be ready to quickly turn your steering wheel the other direction. Might just save your life...

 

[Screendoor]

I knew that it was possible to flip it over. I just didnt know it was going to happen then.

We got a new house and it has a shed AKA my new shop in the back yard. Once we get moved in I am going to take the carb off and see what the problem is. We mover in on the 25th so once we get settled I will take it apart. I have it sitting up on saw horses right now and it looks amazing.

 

[Screendoor]

http://www.ridelust.com/golden-wheels-recall-a-time-when-midgets-were-big/

Anyone know of a company that manufactures kits for open wheel roadsters like these? I have searched and searched with no luck!

 

[anderkart]

I know a guy here in Phoenix that restores and builds "period-correct" vintage Sprint cars, Supermodifieds and Midgets like back in the 1940's throught 70's just like the ones in your link. But you'd be looking at $10,000+ for a vintage-reproduction kit, or much more for a restored Midget from him.

You'd save lots of money just buying an older style Midget and restoring it yourself.
You'll find some for sale in this search link:--> http://www.google.com/search?source...S369US369&q=vintage+midget+race+cars+for+sale

The more modern style Midget racers look simalar to this pic:

 

[dinot71]

When I tune my racing motorcycle is use a color tune on two of my cylinders to try and obtain near perfect combustion at higher RPMS, I wonder how it would work on a single cylinder engine?

http://www.carbtune.com/

After you go to to main page hit the "Colortune" link and you will see how this works. Basically it left you see inside the combustion chamber and when you see blue you are at a perfect state of tune....

 

[devino246]

When I tune my racing motorcycle is use a color tune on two of my cylinders to try and obtain near perfect combustion at higher RPMS, I wonder how it would work on a single cylinder engine?

http://www.carbtune.com/

After you go to to main page hit the "Colortune" link and you will see how this works. Basically it left you see inside the combustion chamber and when you see blue you are at a perfect state of tune....

Or you could just use a $20 vacuum gauge.

 

[dinot71]

Or you could just use a $20 vacuum gauge.

Did you even read what I wrote? Try reading it again....the entire posting this time.