Moderators: notoptoy, garth, S Allen
- Roadster Fanatic
- Posts: 108
- Joined: Tue May 31, 2011 4:51 pm
- Location: Fort Wayne Ind.
- Roadster Fanatic-Site Supporter
- Posts: 6712
- Joined: Fri Aug 07, 2009 11:47 pm
- Location: Tacoma, WA
Later versions came with 34mm venturi vs the early with 37s. People often set the accelerator pump in the bottom hole as the Mikinu accelerators tend to over fuel and that will reduce the volume. All engines vary, so while a change can get you closer, and maybe right on, it may be necessary to try a few different mains and airs to dial it in. Also, without a wideband O2 sensor giving you real immediate feedback, you're going to need to read your plugs and make sure you're not lean or rich. If you don't want to buy and install a wideband (requires welding), then another option would be to get the suggested jets, read plugs and make sure you're OK, and go to a dyno tuning shop and do a test pull with their O2 set up to make sure you're good and safe. They will be able to tell you what it's doing at different rpms and which carb system is operating (pilot vs mains), and likely suggest a step or two in either direction for jet changes. I suggest you familiarize yourself with how the carbs work in general via a mikuni manual or off the internet. All this is optional, but worth doing in my opinion. You have installed a system that is more tunable (Mikuni vs SU) but to get the best results ya have to tune IT!
To give you an example of why I love having a wideband, yesterday I was out breaking in my new engine and noted a stumble at times. I could immedialty look at the wideband and see it's a lean stumble, and it has to do with my accelerator system needing adjustment (not enough response) as the jets quickly catch up and air to fuel ratios go back to where I want them... There's a lot less guessing about where or what to tune, and I will be able to see my results with each change. After so many years of jetting carbs by reading plugs, this is awesome.
Hope that helps!
'67 2000 #588
- Roadster Nut-Site Supporter
- Posts: 1421
- Joined: Sat May 02, 2009 1:54 pm
- Location: Catoosa Ok.
- Model: 2000
- Year: High Windshield-68-70
1969 2000 solex mine since 1972, under resurrection. (Finally resurrected as of spring 2019!) 1969 Porsche 911s -worth more, but not as valuable! (Soon to be resurrected)