bob_nj

My Feedback: (62)

I was having some idle issues with an "almost" broken in Syssa.
I would have to leave the idle around 3000 rpm and after about 20 seconds or so like on final,
the rpm would just drop out, and sometimes the engine would just die.

I twiddled and tweaked the needles, tried different prop loads etc. to no avail.
The ignition seem to be a newer style RC Xcel, so it's not one of those #4's with no curve.

I decided to check the pop off pressure and was surprised.
My gauge goes to 30 psi and the carb still wouldn't pop.

I checked and adjusted the metering lever height, put a kit in it and tried again, same thing.
Got the old Walbro spring kit out and tried a couple of shorter and lighter springs but same thing, 3o psi and no pop.

Decided to run it just for kicks and it did seem better, but it still bugs me that I can't get it to pop.
Every carb I've ever adjusted would go off between 12 and 15 psi.

Can it be something with the accelerator pump feature of the Syssa carb?
I didn't see anything different in the carb that looked like a pump though.

Thanks for any ideas
Bob

ahicks

My Feedback: (2)

No experience with pop off pressures. Thank God I've never had to visit that. I look to see if the lever is level with that raised reidge, then move on.

What I wanted to share was I think that if you have taken the potential for the ignition to be causing that problem out of the picture, it's almost guaranteed that your low speed is too lean. If it's not the low speed needle causing it (which would have been my bet), there's also the possibility you could have a vacuum leak? Could be anywhere in the intake path, crankcase, or cylinder to crankcase joint? Sometimes you'll see a fuel stain at the leak, but not always.

Have you set the low to 1.5 and the high to 2 turns (WAY FAT), then start your carb adjustment procedure over again?

Maybe something to think about if you haven't already. Best of luck!

bob_nj

My Feedback: (62)

Thanks for the thoughts.

I adjusted the low end from one end to the other with no change.
All of the gaskets seemed to be OK when I took the carb off.

I ordered some spare parts from Syssa but don't expect an acknowledgement to my order till Spring or better.
Their service is horrible.

Take care
Bob

captinjohn

Just a Idea....try another carb with about the same size throat. Most all carbs have the same bolt-on pattern. At least then you can see if that helps....untill you get another carb or parts to correct the one that came on the engine.

Capt,n

soarrich

My Feedback: (98)

That would seem to say you have a clogged low-speed jet. You should be able to make it super rich. I'd take the "L" needle out and put some high pressure air to it, (where you take the needle out).

bob_nj

My Feedback: (62)

I think I have an old DA50 WT carb.
Just thought that would be too much for a 30cc?

soarrich

My Feedback: (98)

If it's a reed valve engine, (I forget if it is), they are very tolerant of too big of carbs.

Truckracer

My Feedback: (19)

I really didn't care for the WT 813 carb on the Syssa I owned. Mine also developed a similar low speed problem that I could not resolve. This carb is a bit different from non-accelerator pump versions as there are several parts built into the main body of the carb to make the pump work. This includes a non user replaceable one way valve that on my carb seemed to deteriorate. I thought that maybe some pieces from this valve got into the various low speed fuel passages causing problems. I pretty much left it at that and simply changed the carb to the one used on the current Zenoah G-26 and never looked back. Sorry, I don't remember the WT model number for the carb as I am at work and don't have the info here. Another good carb choice might be the one from a DLE30. Even when it was working OK, I didn't like the WT813 mostly because of the accelerator pump. I know some people like this carb, I did not.

Even later, I replaced the Syssa with a DLE30 .... and never looked back. The DLE just fits my preferences better and in no way am I putting down the Syssa as it is a very high quality engine.

bob_nj

My Feedback: (62)

Thanks Truckracer

It's good to hear that someone else had a similar issue.
Thought I was losing my mind.

Suposedly a Walbro 645 works ok.
I'll wait to get one from Syssa and see how it shakes out.

Thanks
Bob

Truckracer

My Feedback: (19)

The WT645 could be the carb I used, I don't remember but will post the number later on.

I also just remembered that when my problem developed, the high speed needle adjustments were also less effective. Fyi, the carb screen was always perfectly clean so no outside crud got into the carb.

Antique

My Feedback: (4)

The accelerator pump is a little plunger that fits into a hole under the carb shaft...The shaft is milled halfway across to push the plunger as the shaft rotates...It's not really necessary on a 2 stroke gasser engine, it's made for a chainsaw where the trigger is pushed faster than the throttle on the plane...
The 201 carb from a DA 50 would work, so would a WT76A or the 645 carb from a G26.....

bob_nj

My Feedback: (62)

Thank you sir!

So could the pump be the reason it doesn't pop like a non-pumed carb?

Truckracer

My Feedback: (19)

The pump (not accelerator pump) side of the carb and the needle valve under the demand diaphram is exactly like any other Walbro carb. I wouldn't think there would be any differences from any other Walbro in this area.

Truckracer

My Feedback: (19)

As part of the accelerator pump, there is also what appears to be a small one way valve under a welch type plug with a hole in it. These parts are under the diaphram in the main body of the carb. This part doesn't exist in other non-accerator pumped Walbro carbs. This is the part that seemed to be the problem on my WT-813. Looking into the hole, what appeared to be a rubber valve seemed to be in pieces.

Antique

My Feedback: (4)

The one I have here is a WT624..Under the extra welch plug is a very fine screen, no rubber pieces anywhere...the hole leads to the center of the venturi, before the other small holes that control the idle and mid range mixture...

bob_nj

My Feedback: (62)

This is good stuff!

Truckracer

My Feedback: (19)

Ralph, on the WT813, the hole I'm talking about does not go to the venturi .... and I know about the screen and plug you speak of. That is the same as on the WT-76, etc. that use the fine screen in place of a high speed check valve. The hole in the WT-813 is off center from the venturi. Though interesting, I don't know that I care much about this though as I really didn't care for this particular carb, the way it needled or the accelerator pump.

w8ye

My Feedback: (16)

Most of the people that jack the throttle a lot in a hover do not like the 813 because of the accelerator pump

bob_nj

My Feedback: (62)

Wonder why that was the carb of choice?

Truckracer

My Feedback: (19)

I don't jack the throttle around like that very much so that wasn't a real problem for me. I just didn't care for the way the carb adjusted even when it was working well. By contrast, the various carbs used on the DLE engines as well as something like a WT-76 have needles that give clean changes when they are adjusted. When you turn a needle, you get a result. On the WT-813, the needles were vague and seemingly without enough range of adjustment. Maybe that was because the carb was poorly matched to the engine and not really the carbs fault but regardless the combination didn't seem to be a good one. By contrast, the carb from the G-26 adjusted very well and worked great.

My guess is that one of the main reasons the WT-813 was selected for the Syssa was that it was simply available and probably at the right price. Many Walbro carbs that will work for our engine applications are simply not available. Others may not be available in the right quantity or at the right price. Many carbs we use are long since discontinued and may only be available from old warehouse stocks .... which means limited quanities. Why Syssa chose the carb they did is just a guess though. This would be a good question for Mr. Syssa!

pe reivers

I checked many walbro carbs. My gauge goes to 40 lbs pressure. Sometimes that is even not enough, and the carb pops at about 50lbs. Still they work fine. Pop-off is not as critical as some know-betters want to make you believe. As long as the needle re-seats well, the engine will run satisfactory if the needles are tuned.

w8ye

My Feedback: (16)

What's important is that it re-seats above 10 lb

pe reivers

I like them to re-seat at 20lbs or more. This has always provided a very stable idle.

Antique

My Feedback: (4)

The WT 813 was originally calibrated for a Zenoah G260 PUH helicopter engine.....The needles might be the finer thread mandated by the EPA so us mere mortals can't adjust the carbs easily...the fine thread needle carbs sometimes take 4 turns open to be right...Blame the EPA...Not the carb...
FWIW if you actually do a Google search on the Walbro aftermarket site you will see the needle thing on the first page....

bob_nj

My Feedback: (62)

So Pete

What would one have to do to get a higher re-seat pressure?