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mini t
Samba Member
Joined: March 19, 2018
Posts: 60
Location: Michigan
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 Posted: Wed Jan 11, 2023 12:00 pm Post subject: Hesitation off idle |
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so my buggy hesitates of idle i have 1600 single port stock 30/31 solex electronic ignition cant seem to get it to stop hesitating of idle timing is right valve adjusted. any help would be great
thank |
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EVfun
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Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Wed Jan 11, 2023 4:50 pm Post subject: Re: hesitation of idle |
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What distributor are you running? What is the initial timing set too? Is this the buggy with the dual exhaust in your pictures?
I see a lack of working intake preheat. The factory didn't take heat from cylinders 2 and 4. I see a carb known to be jetted on the lean side and not actually intended for your engine. With information about the distributor it may need or vacuum port changes or?
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mini t
Samba Member
Joined: March 19, 2018
Posts: 60
Location: Michigan
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| Posted: Thu Jan 12, 2023 9:42 am Post subject: Re: hesitation of idle |
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i have a 1970 1600 single port running a stock dizzy with conversion yes its has the duel cannons timing set at 30%. what should the jet size be? i do have heat at the manifold.
heres a pic of engine also |
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oprn
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Joined: November 13, 2016
Posts: 12744
Location: Western Canada
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| Posted: Thu Jan 12, 2023 4:36 pm Post subject: Re: hesitation of idle |
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All you will get out of those pipes and the heat riser set up like that is a bit of back and forth at idle at the ends and virtually nothing in the center of the intake where it counts.
What is your ambient temperature right now? What is the timing at idle with the vacuum port on the carb plugged? Is the distributor vacuum pot diaphragm still good? Are you using the correct spark plug heat range? Do you have a thermostat and does it work correctly? A cold engine is hard to tune. I spent 6 summers trying to tune a cold engine and fixed it with a thermostat install.
Sweet looking Buggy, I like the color!
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EVfun
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Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Thu Jan 12, 2023 7:05 pm Post subject: Re: hesitation of idle |
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| mini t wrote: |
i have a 1970 1600 single port running a stock dizzy with conversion yes its has the duel cannons timing set at 30%. what should the jet size be? i do have heat at the manifold.
heres a pic of engine also |
I see a few things to check.
What are the numbers on the distributor? It looks like a stock distributor, but these changed almost every year. The distributor you are running will effect how the timing should be set. Since you are open in a buggy I would suggest running more advanced than VW called for, but that might mean running around 5 degrees advanced or around 12 degrees advanced. These numbers are set at idle with the vacuum port disconnected. and plugged.
You have a non-original carburetor sold as a universal replacement. It may need a rebuild or may have a worn out throttle shaft. A worn throttle shaft would leak in extra air that isn't metered for fuel. Since the H30/31 is already pretty lean that would make any hesitation worse.
It looks like you have a small air filter right at the top of the carburetor. The stock oil bath air filter functioned as a velocity stack and not having that can effect air/fuel mix. Can you fit a stock oil bath filter up there? It may help, or may be too slight to notice.
That next potential issue I see on the intake is a lack of warm air for the air filter. This is a harder thing to fix on a beach buggy. If you only use it in warmer and dryer summer weather it's not much of an issue, but colder and/or more humid air really makes warm intake air more helpful.
The heat riser is working, you have observed, but Oprn hit the nail on the head. At idle the hot exhaust is trying to flow one way for about 0.1 second and then the other way for 0.1 second. At 3000 rpm it is trying to reverse direction every 0.04 second. That tends to cut the applied heat way down. There have been aftermarket exhaust systems with scoop in one end and reverse scoop in the other to enforce a flow in one direction. I haven't seen it in a dune buggy dual system.
That gives you a few places for improvement. Not all should be needed, and to some extent it is possible jet around not having ALL the issues fixed. These running issues can be worked out with some of your effort and a few changes. If you don't know the history on that carburetor it may be easiest to start with a good rebuild from one of VW specialist, like Volkzbitz. (I've used his services and was happy. I tend toward mostly stock engines.)
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| As a general rule, cheap parts are the most expensive parts you can buy. |
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mini t
Samba Member
Joined: March 19, 2018
Posts: 60
Location: Michigan
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| Posted: Fri Jan 13, 2023 9:51 am Post subject: Re: Hesitation off idle |
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Im in Michigan but only drive it during the summer so temps are around 70 -90 deg, vac is good, plugs are what the book calls for ngks, no thermostat.
it is a stock dizzy 205 T with electronic conversion carb is a solex 30/31 that is only about 3 years old from buying it rebuilt, don't have room for stock air box.
i have a complete set of weber 34 ict, and some weber 40mm but no manifolds what would be the best do center mount manifold and single 40mm or the 34 ict |
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EVfun
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Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Fri Jan 13, 2023 3:47 pm Post subject: Re: Hesitation off idle |
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Dune buggy duals with dual 1 barrel carbs tend to be a problem, leaving you with a rough idle and low end running difficulties.
With the distributor you have my guess is you need to advance the timing. I recommend you set the timing at idle, with the vacuum line disconnected and plugged. Sock would be setting it at Top Dead Center (0 degrees advance), but I would suggest about 5 degrees of advance in an open installation like a buggy. Then reconnect the vacuum line and test it out on a warm day. Your distributor should give 32-35 degrees advance max. Setting the timing to 30 degrees at 3000 rpm no load with vacuum connected means you may be running with the timing after TDC at idle. The Bug engine tends not to like that.
The other thing I would consider is some way to lengthen the intake above the carb. I went with a Bus elbow because my Mini-T offers no room above the top of the fan shroud. However, the body on mine sits very close to the alternator pulley. The type of fan guard you have on your buggy would not fit between the alternator pulley and the body. It is hard to know how much this will help, but it can help some. The timing should be a bigger deal.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12744
Location: Western Canada
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| Posted: Sat Jan 14, 2023 5:33 am Post subject: Re: Hesitation off idle |
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| EVfun wrote: |
| Dune buggy duals with dual 1 barrel carbs tend to be a problem, leaving you with a rough idle and low end running difficulties. |
^^^This!^^^ You have no idea what poor running is until you have experienced dual singles and dual cannons!
Stop blaming the cab until you have done what EVfun says below. I would bet the farm on the timing being the main issue... and a cold intake.
| EVfun wrote: |
| With the distributor you have my guess is you need to advance the timing. I recommend you set the timing at idle, with the vacuum line disconnected and plugged. Stock would be setting it at Top Dead Center (0 degrees advance), but I would suggest about 5 degrees of advance in an open installation like a buggy. Then reconnect the vacuum line and test it out on a warm day. Your distributor should give 32-35 degrees advance max. Setting the timing to 30 degrees at 3000 rpm no load with vacuum connected means you may be running with the timing after TDC at idle. The Bug engine tends not to like that. |
I am with EVfun here on your problem being mostly timing. I would go even further and set the initial at 10 to 12 degrees and get in there and limit the total advance to 30 to 32 degrees. Check your vacuum can, it should be giving you between 9 and 11 degrees additional advance too at light throttle cruise (but not at idle). You can print off a degree wheel on paper for free and stick it to your stock pulley with double sided tape for these tests but you need to find true TDC. Don't trust the stock pulley notch, it could be off any year of engine and there are a bunch of differing marks on them.
| EVfun wrote: |
| The other thing I would consider is some way to lengthen the intake above the carb. I went with a Bus elbow because my Mini-T offers no room above the top of the fan shroud. |
Yes!
That heat riser needs to change too, don't sweep that under the rug!
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age) |
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mini t
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Joined: March 19, 2018
Posts: 60
Location: Michigan
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| Posted: Sat Jan 14, 2023 9:23 am Post subject: Re: Hesitation off idle |
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| thank for the advise, so i'll change the timing when it gets a little wormer here |
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MrGoodtunes
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Joined: May 14, 2012
Posts: 852
Location: South Florida
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| Posted: Sat Jan 14, 2023 9:27 am Post subject: Re: Hesitation off idle |
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| mini t wrote: |
| ... my buggy hesitates of idle ... |
Thanks for changing "of" to "off" in subject line. Now I get it, you have what's call'd "Tip-in stumble" by my engineering friends. They say it occurs when gasoline vapor condenses out from the air/fuel mix onto inside walls of intake manifold, making those walls sort of wet with liquid gasoline. The primary solution is to heat up your intake manifold. It's also helpful to create a velocity stack above carburetor intake, 'cuz this encourages smooth laminar flow thru intake (versus turbulance, which sorta throws gas out to sidelines).
Surprising Story:
I was trying to make sure my aftermarket air cleaner fit my carburetor better, i.e. without leaking. (See: Tiny hole directly above funky old hose clamp center of top left pic.) Bought a drain plumbing connector at Home Depot, and cut it up to do the job. It ended up giving me a short little velocity stack. So that while achieving my leak-free goal, to my amazement it completely cured my rare occasional tip-in stumble, plus smooth'd idle enough for me to lower it below 700 RPM.
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mini t
Samba Member
Joined: March 19, 2018
Posts: 60
Location: Michigan
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| Posted: Sat Jan 14, 2023 9:59 am Post subject: Re: Hesitation off idle |
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| thanks for the idea will maybe look at some thing like that to help |
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