Today's solex maintenance ...

[Down under 311]

Ok gave the car a tune up with colour tune during the week and although it's idling quite well and pulling well to about 5 k it seems to run lean or restrict after that.... In tuning I noticed the front cylinder could not be adjusted to run rich.. Am I right to think the pilot jet maybe blocked ? Anyway in looking in the carny there was a fair amount of grit in the bottom - not huge amounts but enough to think this afternoon will be a compressed air clean up....
I am also going to check my jetting ... Although it was initially set up by local guru alistair.. After reading all the info on line just want to check the difference between the fuel and air jets...
Interestingly my spare set are running 170 fuel 225 air and 57.5 pilots .... Not sure on the Venturi size (where should that be shown?)
Anyway I will update after my maintenance run and see if I can't get them running properly... I'm guessing my blockage will be the main problem with the rev range as well...

Wish me luck and of course any suggestions welcomed !!!

[Gregs672000]

I don't currently run solex or Mikuni, but am familiar. Hard to say on your jetting. The pilot jet is probably about right. The others are larger than what I have generally run with the newer Mikuni, but sometimes it is also a matter of how the jets work together with the emulsion tubes you have, and possibly what version of carbs I would imagine too. And choke size... Look down the front throat of the carb and you will see the choke, and on it will be a number, like 37, or 34, etc.

The BEST money i have spent, and what has changed everything in carb tuning for me is getting a wide-band A/F meter. They are so cheap these days, they will save you so much time and effort you will never go back to guessing on what the motor is doing. TRUST ME ON THIS! You could also set it up as something for other people to borrow, as all you need to do is weld in a bung in the exhaust collector and it can be used. But I love having mine... Check the gazillion posts, read "40mm chokes, OMG!"

[Down under 311]

Greg - got my eyeon one at te moment ... Think I'll take the plunge and buy one ... Havnt checked the car for what's in it but dont think they are as big as my spare carbs ( bought second hand so don't know anything about why they were jetted accordingly...

Interested to see the combination in the car - will check when I get home !

Bit hard to see down the throat due to the uni filter air box but I'll see how I go ..

[SLOroadster]

Ok, lets start at the beginning. What version Mikunis do you have? Type 2s or 4/5s? From there, what jet blocks are you running? Looking at your jets, depending on altitude, they are looking lean on the top end to me. From the sound of it, it pulls fine for the first 20% of the throttle which means its likely not the pilots that are the issue. How many turns open are your pilot screws? If you are more than 2 turns open, you have too small pilots. If you are running an A cam, with 34mm venturis, you might be ok. A B cam and 37s, odds are they are they are a little lean. (Perhaps, depending on altitude.)

Looking at your mains, they are going to be lean up top, where you are running into the issue. Based on your fuel jets being a 175, you want 200 airs, perhaps 210s depending on the car.

From the sound of the symptoms, your pilots are fine and your main airs are too lean. If you have more than a B cam and are running only 34mm venturis, this could also be the issue, but will require both a change in venturis and jets.

Will

[Down under 311]

Ok they are late model solex's 5 I think
8 tubes
55 pilots
150 fuel
150 air !!!!
Ok now that's got me stumped .. ?
Firstly will the series 1 jets I have fit the late model solex .

Its an Aussie 150 hp so be cam etc standard 68 model !

[Down under 311]

Ok swapping the spare complete over to the car to see where that sits !

[Down under 311]

Ok so an interesting night...
Pulled out each of the jets and as mentioned fuel was 150 same as air! So not good really from what I have read ... Then to make things worse 1 cylinder was 180 fuel ... No wonder first always seem to run rich !!

So I decided to swap my spare set into the car ... So as mentioned pilot 57.5 gas 170 and air 225 ..
The result ... Way more responsive ... Too much wheel spin down low !! but has been mentioned hesitant around 5-6 k perhaps lean ?? Still not sure about the venturis - hard to get the filter off. But may have to do it I guess..

Found a place in oz that supplies mikuni jets... So please give me idea of the range I should get !
Thanks for all your help....
Cheers

[SLOroadster]

Try leaving your fuels where they are at and dropping down to 200 airs, perhaps even 195 airs. That should fatten things up at the top end a little.

The #8 jet blocks are correct, 57.5 pilots might be ok, as I asked before, how many turns open are they? If you have a small mirror, shine a flashlight down the throat of the carb and see if you can see a marking on the edge of the venturi. If the venturis look really fat, they are likely 34s, the 37s look proportional to the carb, larger than 37s start looking small in there.

Will

[Down under 311]

There about 2 to 2.5 open I would guess .. I'll order in some 195 200 and 205 maybe to play with...
I have a unifilter air box on it that is a bastard to get on and off so it's had to see down the throat as I have maximum size ram tubes inside the box.... I looked at my spare set and couldn't find any numbers ? Does a series 5 normally come as a 34? ... I'll try and have a look tomorrow...Do you have a photo of what 34's look like or the 37s as well ??

Like the 57.5 pilots _ gave it a lot more up and go...
Thinking I'll get the 02 sensor put in as well to get it right. But that may take a couple of weeks

Thanks very much for your help!!!

[Gregs672000]

Will is guiding you well. The original jetting I got on my last set of newer Mikuni was screwey like that, so I am not surprised. They also came with 34mm chokes or venturis. I think all the later ones came that way.

Glad you're getting the Wide-band... you will absolutely LOVE it. I got an inexpensive one by Glowshift (http://www.glowshiftdirect.com/wideband ... auges.aspx" onclick="window.open(this.href);return false;) but I think I paid more like $130. Check online. Regardless, well worth the money!

[SLOroadster]

We really need to know what size those venturis are. Venturi size is part of what dictates the main fuel jet size, and from there dictates the main air size.

I do happen to have a pic of the Venturis. They are out, but here is a 34, 37 and 39 mm (left to right in that order.) You can see the 34s are pretty thick.



If the pilots are 2.5 turns out, you should step up to a set of 60 pilots.

Will

[Down under 311]

Yeah my spare carbs are 34 ... See where there marked now ...
I'll work up the courage and skin tape to get the air box off to have a look !
So pilots 60 then huh!

Wish me luck !

[Down under 311]

Ok so contortioned myself around the tubes with a mirror and yep there 34's !

So currently I'm thinking
60 ? Pilots
170 fuel ( currently in there )
And getting 190-195 airs to play and see !

Sound right ?

[Down under 311]

This is what I mean - but I did manage it....
[IMG]http://i1061.photobucket.com/albums/t46 ... a/c8dc477c.

[Down under 311]

Bugger
Try again