The car's running pretty good, so I've begun my quest to fiddle with it enough to make it run worse. I've been data logging my air fuel ratios at various speeds and engine loads and decided it was pig rich. It is set up with dual Kadron 40s with 130 main jets and 55 idle jets. As I'm sure you all know, but it was news to me (most of my tuning has been fuel injection), the Kadrons run on the idle jets up to 2500-3000 rpm and then on the main jets up to around 4500 rpm and then pretty much depend on the air jets above that. I was seeing low 11s with the 130 mains at full throttle and 11-12s on the idle jets at lower rpm. So, time to play around with smaller jets.

Cheapskate that I am, I checked around for an assortment of jets that didn't break the bank. Thesamba said that Mikuni motorcycle jets were the same as the Kadron/Solex/Brosil jets, and you can find a good assortment of identical jets in smaller sizes than the 130 on Amazon for less than $10. You can also get a kit for PWK Keihin OKO CVK PWM carbs that include "air jets" for the same price. I decided to give the latter a try.

The kit included 10 main jets from size 100 to 140. The PWK Keihin OKO CVK PWM jets have the same threaded part as the Kadron/Mikuni jets but the heads are a bit smaller. I tried the 125 jets and the 120 jets and both worked well. Switching from a 130 to a 125 raised the full throttle AFR by .9. I'm running the 120s right now and seeing full throttle AFR of around 13 at 4000 rpm.  solex vs PWK Keihin OKO CVK PWM

The idle jets in the kit are useless for the Kadron - they are very much the wrong size to replace the originals. It's not worth buying the PWK Keihin OKO CVK PWM kits to get them. Doing it again, I'd just buy the Mikuni assortment.

kits

I looked around for a replacement for the idle jets and there are some on eBay for about the same price that John at aircooled sells his but with free shipping. I figured John has contributed so much of his grumpy expertise to the aircooled community over the years that I'd order the idle jets from him even though it almost doubled the price for shipping (Hawaii problems). I ordered 50s for the idle circuit, we'll see how it goes.

Mike

 

Attachments

Photos (2)

That's really cool. Thrifty and smart.

I have a customer with an 1835 sandrail I work on from time to time. It had a badly worn single progressive carb on it. I replaced that with a dual Solex 35PDSIT kit from John Connelly, among other parts. He jetted them for me and honestly they ran awesome out of the box, all I did was synch them and set the idle mixture.

I bought my recent rebuild parts from him, Mahle P&C, Total Seal rings, etc.....I love the Total Seal tapered ring installation tool. SO EASY to get the pistons installed. Used that on my motor and Brian's 2332.

The shipping is sometimes excessive but the parts are always right. Thanks John.

A couple of small updates:

- Some of you may remember me complaining about crunchiness in the steering. We conjectured about bearings, etc. I finally disassembled the steering to install a new turn signal switch and to rebuild the top steering bearing. When I got it back together, it still had crunchy spots when turning the wheel. I had a "doh!" moment and took a look at the lower end of the steering tube. Sure enough, the column was rubbing on the upper edge of the steering tube. The tube alignment was off because the steering tube, where it attaches at the top (near the steering wheel) needed a spacer to lower the steering wheel. This is one of those things that happens when you buy a speedster completely disassembled by the previous owner or by the forces of nature after sitting near the ocean for 14 years. One small rubber spacer later, all of the crunchiness disappeared! Huzzah.

- I'm getting closer on the jetting for the Kadrons. I've dropped the idle jets size down to 50. This gives me much more reasonable air fuel mixtures during normal low speed driving. Unfortunately, I had changed the main jets to 120s.  This gave me full throttle AFRs in the 13s between 3000 and 4500 rpm, but gave me a huge lean spot between 1800 and 2500 rpm on partial throttle.  It's obvious that main jets can have a big impact on Kadrons below 2500 rpm under certain conditions. I swapped the mains up to 125 and then again back to the stock 130s before the flat spot at partial throttle went away. While I was in there, I slightly bent the accelerator tube tips out of the venturi space (up roughly 1/4 inch) and pointed the spray towards the joint where the butterfly touches the wall. I re-positioned the tubes slightly again to make sure they fit well under the carb tops. Once I had them set up so they wouldn't dribble gas at high venturi speeds I tapped the tube base using a screwdriver and a small hammer. That made sure the tubes wouldn't swivel and were sealed to the carb. 

So, I did a rough sync and set the accelerator linkage a little bit richer and took it out. It's running really nicely. I can't feel it with my buttometer, but the AFR logs say I need to dial the accel pumps back just a hair (getting a drop down into the 6-8 range right after I punch the throttle).  

With the alignment (THANKS for the help with specs), the front and rear sway bars, oil shocks up front and the engine losing its flat spot, I'm grinning like an idiot most of the time. 

Mike

 

Mike, dial those accel pumps back until it falls on it's face, then open them a tiny amount. You want the minimum accel fuel spray until the fuel gets drawn from the well by the speeding-up air. That's how I set them.

According to John Connelly from aircooled.net, it's OK for it to run lean at part throttle, up into the 15-17 range. There are some AFR threads on thesamba.com. Good reading. Cheers, glad you got it running well.

Add Reply

Likes (5)
MisteplicKaryadiAllnuttSTededsnova
Post Content
×
×
×
×
×