Interesting design

[Doc Sprocket]

Sorry, off topic post, but you should start a thread with some model pics. I just got into it a year or so ago and have built a few.

Hey, GREAT! Yeah, I gotta try to dig some stuff up! I haven't worked on any in awhile (was kind of like writer's block), but I'll get back into it. I love kitbashing! I'll rape 3, 4, even 5 kit boxes for the parts I want to use on a build.

We'll revisit this in another thread. And now, ladies and gentlemen- Back to your regularly scheduled thread! (sorry for the OT stuff!)

 

[dmaznic]

I'm debating at the moment about heavier springs.
-Are there any advantages to stiffer springs if I don't care to increase RPM too much?
Top safe RPM might actually REDUCE with stiffer springs using stock cam rods. The cam rods are subject to more stress with stiffer springs and could fail at lets say 4500rpm. On the other hand, lighter stock springs may allow up to 5000rpm until the valves begin to float.
-any suggestions ?

 

[Doc Sprocket]

Yeah- Upgrading your valve springs should be one of the LAST things you modify internally. Upgrade everything else first, using your stock springs as a safety margin.

 

[dmaznic]

New pictures:
http://toronto.kijiji.ca/c-cars-vehicles-other-2012-ruli-kart-made-in-Canada-W0QQAdIdZ386568168

I tried to show some of the drive/suspension details. I hope to make a video of it running this weekend. <still waiting for that jet order grrr>

 

[dmaznic]

Just ran it after the engine mods.. WAY too lean. High flow intake, high flow exhaust, exhaust insulator and governor removal--all under standard #72 jet, #90 still on back order :toetap05:

I feel a lower gear ratio will be better. Before and after engine mods, the engine speed was 2900 max. Granted it will improve with a bigger jet but I want to go comfortably to 4000rpm.

Chain was falling off a bit too. It's almost inherent to the design. It is possible to alleviate this problem by tensioner adjustment and slightly different sprocket allignment.

Will keep posted!

 

[dmaznic]

needless to say no video was taken

 

[Doc Sprocket]

2900 RPM? Way too low- is that measured or estimated? Any idea why it is so low, and have you attempted to adjust it to at least the normal 3600?:

 

[dmaznic]

yea, measured with a digital tach while riding. Idle was just about 1800 rpm so it's probably right. The thing is without the bigger jet, it's having a hard time coughing up the extra power and begins to stumble. Also, gearing is 6.1:1 but the wheels are 16in. I just bought a sprocket that will let me go to 7.8:1 but Im not sure if I'll use that specific one.

--what are you guys using for chains?
Mine is #35 from princess auto and sometimes I get problems with cracking

 

[Doc Sprocket]

#40 would probably suit your needs better. I use #50- which is overkill- but that's me.

If you are peaking at 2900 RPM, you're missing out on a LOT of potential. Sort out your jetting, and if that doesn't get you bouncing off the governor, re-gear.

EDIT- Little confused here- I just checked your ad- says 4500 RPM, top speed 55-60 KM/H. But above you say you're topping out at 2900 RPM.

I just buzzed the numbers thru my speed calc. If you're topping out at 2900 RPM, your top speed will be around 37 KM/H. At 3600 RPM, top end should be around 46 KM/H. At 4500 RPM, you should hit close to 57 KM/H.

 

[dmaznic]

yes, sorry for the confusion, so 55-60 km/h is the ballpark speed at 4500rpm. This is my estimate. The tunning is not fully done but I needed to get the ad out there for the summer. If it comes down to it and I can't improve the engine response, I will update the ad accordingly and take my fall on the sale.

I'll keep everybody posted Im thinking to stay with #35 to keep the sprockets. Maybe up the quality of the chain if I can (ps. I will be providing spare chain in any case). Anybody heard of O-ring seal chains? I saw it on motorcycles/ATVs.

 

[Doc Sprocket]

Yes- O-ring is the standard for motorcycles. I don't know if you can get it in ANSI sizes. Don't get too comfortable, though. You've got to sort out the carb, before you can be certain if gearing is appropriate. Refresh my memory- what are your ratios and tire size?

 

[dmaznic]

main ratio is 6.1:1 and interchangeable with 7.8:1 on 16 in tires
the clutch is a standard centrifugal one, engages somewhere above 1800rpm