Dellorto VHSH30.. Need Help

[Steve Libretto]

Im new to Shifter Karting this year, and I have a TM K9B with a Dellorto VHSH30 Carb. I’m hoping someone can point me in the right direction to where I can find info to learn about carb setups. I know nothing about the carb, and have had several people help me get the jetting right at the track, but Id like to learn more about it, so that I understand it. From what it seems like, there are so many things that can be changed to adjust the fuel air mixture throughout the rpm range, but its all WAY over my head.  I do know that it has the “Tek Sav” set up in it now, and Ive run it several times with no issue, but this past weekend I ran in the rain, and felt like it was very lean on the low end. When I get back on the throttle through the turn, it has no response, as if the plug wire was pulled of the plug, then after .5 to .75 seconds, it takes off like a bat out of hell, which in the wet, made for a handful. Any help would be greatly appreciated. THANKS!!!!!!!

Steve

[Thomas Barth]

Hi Steve,

Assuming you were running DQ264/K93/128/CD1/60 jetting, not sure why you had a problem in the rain. I say this because I have never run that set up in the rain. Since you mentioned low end I would suggest that either the idle jet or atomizer were responsible for the hiccup, or maybe the needle height. On the other hand could it have been water getting to carb? The only way to find out would be to change either jet and see what the response was. Of course this is after the fact and not much help.

[Steve Libretto]

Hi Tom,

I have to be honest…. I’m assuming that it is the tech sav set up that you had put in this carb. Maybe it’s time that I take the carb apart and learn a little about it, because I honestly don’t know what those numbers and letters even mean that you referenced in your response, other then the 128 main jet, which I know for a fact is the jet that is in the carb. I think it does something similar in the dry, but much much much less noticeable. It seems to maybe have been way worse due to the extended time off the throttle, and longer deceleration zones from the wet conditions.

[Jason]

Hello Steve,

Check your pilots for a clogged jet.  Check your float heights.  Check the internal fuel filter.

Also, before you go on a wild goose chase for jetting, what RPM”s does this problem start to happen?

 

[Steve Libretto]

Jason wrote:

Hello Steve,

Check your pilots for a clogged jet. Check your float heights. Check the internal fuel filter.

Also, before you go on a wild goose chase for jetting, what RPM”s does this problem start to happen?

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When you say pilots, what exactly am I checking? I know nothing about these carbs at all. Same for float heights…. What should they be, and how do you check/adjust them. Is there something I can read to learn about the carb in general….

As far as what the RPMs were when this would happen, I’m really not sure exactly, but it was definitely in the power band…. It wasn’t as if I was getting a Slow or sluggish response, it was literally as if there was no ignition of fuel, until about a second after my foot had been on the throttle.

[Steen Carstensen]

delete

[Scot Smith]

Hey Steve,  I have had the same problem I think.  Two questions.  Is this a new problem?  Does it do it on every corner or just certain ones?

[Steve Libretto]

Hi Scot,
It is a new problem, but conditions were different also… The race was in the wet… It had just stopped raining 5 minutes before. I did turn my air box around to help prevent direct water ingestion into the carb.

It wasn’t on every corner, but almost every corner….. The longer the decelleration zone, the more likely this would happen. I it was a short/quick brake zone, then back on the gas, it wouldn’t happen

[Scot Smith]

Steve, there is a lot of info on carbs on Tom’s website,  Greenflagkarting.  When I had a similar issue it was only on certain corners and it turns out my outer pilot jet was loose.  Another time same issue and I have seen this two other times for two  different people it was the top of the spark plug being loose(the little thing that screws onto the top of plug) and really dirty where it makes contact with the spark plug boot.  Check that first and let us know.

[Steve Libretto]

Scot, I’ll check the outer pilot jet, but also going to check the top of the plug, since I had changed to. Brand new plug prior to the session I had the issue. I’ll keep you posted, thanks for the suggestions!!

[Oscar Biondi]

Check this out:

http://www.guzzitek.org/documents/carburateur/DellOrtoMAJ01.pdf

[John Savage]

Also read this http://www.karting1.co.uk/jetting-karting.htm

It’s not about your carb but exactly the same principles apply.

 

It would also help you a great deal if you can find someone at your track who runs the same motor and pick his/her brains

 

Jetting and Kart Set-up Software

http://www.rotaxjetting.com

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