TheSamba.com :: View topic

Fri Sep 14, 2007 11:32 pm

Got the motor up and running tonight. For those that remember i built the 2020cc and the bolt got into the motor. Well i went down to the 90.5's after much consideraion and also got the stage 1 tims heads now. I got it running but i beleive the jetting i had before is too big now.
when adjusting the carbs i have the mixture screws turned in pretty much all the way to achieve the highest idle. Im getting slight backfiring sometimes out of the muffler, and it feels fast but slugish.

Current Jetting is 155 mains, 65 idles and 32mm vents. That was what i had purchased from lowbudget for the 2020cc. (i also have the stock jets still, but no idea what they are).

Motor specs:

1955cc
8.9 CR (.040 deck)
engle 120 with aftermarket 1.25's
Tims stage 1 40x35.5's

Valves adjusted, new plugs D7EA gapped .035, CDI ignition

Elevation: 4,668ft

What is a better ballpark jetting to try?

Sat Sep 15, 2007 6:01 am

call lowbugget and ask aj ;)
i dont know personally what it should be but i bet he could give you a good idea

Sun Sep 16, 2007 8:09 am

I think the jetting is wrong.. If these are 40mm Kadrons your going to be like 135 main .55 idle

Im at 4200 ft and have jetted alot of kadrons.. On most 1915s I Use the 1.30 or 1.27 main..

1600cc I use the 120 to 1.22 main this is with stock 40mm Kadron carbs
If you can buy an LM1 and dial it in.. they work so well go for 12.5:1

www.aircooledengineering.com

Sun Sep 16, 2007 11:43 am

You might re-think the vents. You didn't mention what cam you have, but with those heads I would run 30s for the better velocity. At a lower altitude than you are likely at, I ran 55 idles and 140 mains in my 1776 with a 163 Web-cam and CB 044 heads. What exhaust do you have?

If you don't recall what they were, you need to measure any jets from A.J. He tends to re-drill them to get exactly what he wants. Most times he grinds off the original number.

Sun Sep 16, 2007 3:06 pm

Art Thraen wrote: I think the jetting is wrong.. If these are 40mm Kadrons your going to be like 135 main .55 idle

Im at 4200 ft and have jetted alot of kadrons.. On most 1915s I Use the 1.30 or 1.27 main..

1600cc I use the 120 to 1.22 main this is with stock 40mm Kadron carbs
If you can buy an LM1 and dial it in.. they work so well go for 12.5:1

www.aircooledengineering.com

Sweet, thank you for the response Art! Yes these are the 40mm Tb kads. I called yesterday and ordered jets from lowbudget, but not sure what they are going to be.

The previous jetting which was when the motor was a 2020cc with unported heads and 9.1cr and 32mm vents were AJ's 155/65(going off my receipt), now same motor is 1955cc, ported heads 32mm vents and 8.9CR, but I think he does them differently or something based on the #'s. Not sure what Im going to receive but im sure its gonna be better than now.

Car runs ok as of now, but i know its pig rich with the mixture screws turned all the way in, doesnt really want to idle and i have the idle screws turned in all the way too. And being so rich i dont want to drive it too much and have all that gas washing my pistons and cylinders.

Carbs and jetting have always puzzled me, because i dont really have a clue what the idle jets do or rpm range they satisfiy and same with the mains, if that makes sense.

I wouldnt mind buying an LM-1 or using one. So when using an Lm-1 12.5:1 is this the # you want through out the whole RPM range?

Sun Sep 16, 2007 3:13 pm

Oh ya also, anybody have a clue what jets "normally" come in a new set of brosal kads from the factory? Just curious if anybody has measured their "stock factory" jets. I would like to know so, then i could have some jets to play around with. Then Ill have "stock" jets, the 155/65's that are in it now, and i will also have my new jets i ordered. then i could have a cornicopia of jets, lol.