Tillotson HL304WXG Carb Problems

[Scott Kneisel]

Has anyone had any issues using the HL304WXG carbs running WAY too lean on gas?
This is the 3rd one I got from EC where the drillings for all the jets, low speed and high speed were significantly smaller than the 304E or any HL250 or 227.

I talked to EC and they said they should be correct but I needed to have the HS and low speed needles out at 4.5 turns HS and 3 turns low speed and the plug was still almost white. SCARY.

I ended up drilling all the holes comparable to the HL250 and now they work fine. The needles need to be out further than the HL250 because the tapers are longer but now they are reasonable at about 2- 2.5 each, plugs are brown to black like I like them.

Anyone have a similar experience? I am running single carb installation, pump gas on 2ea Mc45's and one on an Mc100.
Scott

[Rob Voska]

You talked to EC? Now that's scarry. He's been dead for years now!

What does the EXG stand for? Of course everything is set up leaner for polution control.

I'm havin gthe same problem with old 227;s. I just think they have the wrong pattern for the fuel requirments for Mac''s.

[Scott Kneisel]

Rob,
The HLWX carbs are supposed to be "builders carbs" with pilot holes for jets so the builder can drill according to application. The HL304WXG is supposed to ve set up for gas and the HL304WXA is supposed to be set up for alcohol. Not sure about the alky carbs but the gas versions are definately set up too lean.

The HL250, HL227 and the HL304E carbs should all drilled the same and have worked pretty well on gas for me. Mike and I were out at the track the other day though and his HL227 on his Mc90 was definitely running lean. He said he was not able to get the engine to 4 stroke at all with the normal set up. He finally raised the fulcrum up pretty good, richened the low end and opened up the HS screws to about 2.5-3 turns and she finally burbled a bit at the end of the straight. He was smoking like heck in the low to mid range though. Maybe that 227 is drilled differently.

I still like the hL250 the best of all the carbs, they seem just right for a Mac. The HL304E carbs work pretty well too. Both are of the original classic body design. I don't know if these newer Infinite radius carbs are suited well for macs although Steve O says he has good luck with the HL334 carbs. I have not tried one of those yet. I now have over $360 invested in the 3ea HL304WXG carbs so now that I have them working pretty well I will stick with them. I just drilled ALL the low and HS holes the same as specified in the older TECH manuals, left the dump hole alone. Installed a new soft plug (these take 1/2" plugs). And they tuned pretty well. Tapers on the screws are longer so they need to be out there a bit more.

Fun,Fun,Fun

[Rolf Hill]

Scott,

MY "problem" was with the 304E! I had a pair of 304WXGs on my 91B1 and did not have a problem. When I put a pair of new, 304Es, straight out of the box on another 91B1, I went with what I knew ... Which didn't work. Currently, the 304Es are at 2+ on the L and 1-1/2 on the H.

What ever happened to the L being in more than the H?

[Doug Tenney]

Interesting that nobody here mentioned lowering the pop-off setting. I resorted to lowering the pop-off pressure on my son's US820/dual HL's (on gas), and now the carbs are able to flow enough fuel to reach 4-stroking. I don't recall the HL numbers (274? 278?), but they're old. I bought the spring assortment kit from EC Distributing (a bit salty for two thimble-fulls of TINY springs, but oh well).

[REAR]

Scott did make mention that Mike raised the fulcrum arm which in effect reduces spring pressure.

R.E.A.R.

[Scott Kneisel]

I should have mentioned the POP.
I lowered the POP on the XG carbs down to 8PSI and raised the fulcrum height until the needle just barely sealed but that didn't work either. Opening up the jets was the only thing that worked.

Recently when I tore down the carbs to clean them out for winter I found that the gasket under the pump diaphragm (single stack carbs) was thinner than normal so I installed the high capacity pump gasket offered by EC carbs in all three carbs. Low pump capacity may have added to the lean condition issue. I did notice that the carbs were slow to pump up from a dry condition but didn't think much of it. Now I will be watchful of those thin gaskets.

I also should say that Mike sets his POP at 8-9PSI on his HLtillys. I usually set at 10PSI open and around 6PSI close on the gas carbs.

[Rob Voska]

Scott, I'm not saying a thicker gasket does not hold more fuel but the problem lies in the drill pattern. It's simply to lean for our needs.

Also I have been thinking the HL227 with the brass tube down in the throat of the carb is designed to lean the fuel curve for high end. Those carbs were for 100cc K78 style direct drive motors and they run very lean on high end.

[Scott Kneisel]

Rob,
I agree, that is why I drilled out all the holes to match an HL250. The WXG carbs work well when you do that, the extra pump capacity is just an additional safety factor.

That 227 tube may not be the hot tip for Macs? Maybe it should be plugged?

[Rob Voska]

I think the pumper plates are slightly different with it's own vent hole. Have to get air on top of the pumper somehow.