Carbs...carbs....carbs...

[viclioce]

Been dealing with Alan & his Wombat 94 via messenger.

He has a Model 94 that ran OK for a while and then stopped running well.

Slow but consistent investigation led to discovering that he had a 93B Super Rat 24mm carb and not a Wombat carb on this 94.

Changing the jets wasn’t producing the desired effect. I kept going back to Terry’s website and confirming what a Wombat 94 carb was SUPPOSED to have in it.

Turns out the slide was a 2.0 instead of a 2.5, so it was adding too much air making bike run lean & idle way too high!

Changed the main jet to the stock 160, pilot to 25, slide to a 2.5 and left the needle to match the main jet. And Voila! Now she runs correctly again.

Similar situation as I had with my Wombat with a Rat carb. Got the main down to a 140 and it dropped right in like nothing was wrong any more.

The only thing I can’t figure out? Why does the motor initially run OK, but then performance drops off until it won’t run any more. Seems like it should have run poorly from the beginning with the carb not being correctly configured. Any guess why this situation occurs? And I’m asking about performance and not “because the DPO did it.” Victor

[Dale]

Huh, the 2.5 slide is leaner than the 2.0.

If something runs fine and then it doesn't, and you haven't drastically changed temp, humidity or elevation (or fuel mix), then it is not due to the carb configuration.

[viclioce]

Well, Dale, in both cases that didn’t prove to be true. Don’t know why. Just know it did happen. Victor

[Dale]

Not buying it. Have him measure the cutouts or at least compare them. 2.5mm is greater than 2.0mm and allows more air which equals leaner. The only way that the 2.0 can be leaner is for someone to have modied it (which was not uncommon back in the day).
I think that there is more going on here.
Was more than one thing changed at a time?
You said that it made it idle too high. Idle is mostly impacted by the pilot and air screw. Yes, the slide will have some impact on idle but has more influence off-idle.

[viclioce]

The carb is a 93B Super Rat carb. The 2.0 slide would not drop down in the slide tube and sat almost 3/8” too high. So the bike was staying at high rpm the minute it started. It would start, but the rpm would not drop. Changing to the 2.5 slide, you could see it drop down to where I’m used to seeing the slide show up.

The 94 Wombat calls for a 2.5 slide not a 2.0, while the Super Rat calls for a 2.0 slide and much bigger jets. The bike was a DPO bike. It didn’t have the VM24 SH-83B carb which was original to it.

So I had Alan change the carb to match what the 83B called for, except leaving the needle to match the needle jet. So it got a 160 main, a 25 pilot, a 2.5 slide and left the 4D3 needle with the N8 needle jet. The bike ran great! He did several laps around the track and it ran and sounded like it should.

Tomorrow, I’m going to have him clean and build to specs a VM24 SH-83B carb which he removed from another 94 Wombat. Then we will try the SH-83B carb on this Wombat and see if there are any performance differences!

Like I said, I have a Super Rat 93B carb on my Wombat. It ran great when Greg sent me the carb. The bike ran great with the carb as sent, but the bike sat for awhile and then all of a sudden it wouldn’t rev properly. So I read the specs for the Model 94 SH-83B carb. I had the 2.5 slide, but the main jet was too big, a 180. I slowly lowered the main in increments of 10, until I got down to a 140 main. Now she hums sling nicely and revs up as it should rather than bogging down, or 4 stroking, I think some folks call it. I haven needed to change anything.

I’m at a 140 main because I’m at 7,000 feet in elevation. We left Alan’s main at 160 because he is at sea level. So that’s the only difference.

Alan did like 3 laps on his backyard track and the bike ran flawlessly. Victor

[taber hodaka]

The throttle valve cutaway basically affects 1/8 to 1/4 throttle. So many factors involved here, Compression, modified in any manor, quality of mix oil, spark plug heat range, air filter, elevation, humidity. Running correctly by who"s standards the beginner, experienced owner, the racer or a professional tuner, factory settings do not give professional results. ---------------------- Clarence

[Bullfrog]

The following statement is not correct:

"Turns out the slide was a 2.0 instead of a 2.5, so it was adding too much air making bike run lean & idle way too high!"

The 2.0 slide is RICHER than the 2.5 slide (assuming both slides are in stock condition).

The operating characteristics of the system simply do not change due to the passage of time. However, it seems apparent that something did change - my best guess is that a bit of flotsam plugged the pilot jet as running time accrued. While chasing that problem by changing other things . . . pilot circuit plug also happened to get removed and things got better. NOTE: A plugged pilot jet makes things leaner at ALL throttle settings (which could have caused the misunderstanding/mistake regarding the slide).

Does the machine have an in-line fuel filter? If not, installing one is highly recommended.

Ed

[viclioce]

Machine has an in line fuel filter. It also appears that the 2.0 slide was not traveling all the way down, possibly a binding return spring. It’s hard when troubleshooting in British Columbia when you’re in New Mexico. But I’m sure you can all appreciate that.

The best thing I can offer is I had Alan completely clean the carb, including the choke pathway. The slide which Alan told me was a 2.0 slide looked physically shorter than his 2.5 slide. Possibly he misread the slide and it was a 3.0, I keep telling Alan, “I don’t know because I wasn’t there.” So I can only report the information I was given.

But the previous slide was, indeed, much shorter than the 2.5 slide he changed to. That much I could tell because he photographed them side by side. It doesn’t mean I’m wrong, it means I was given the incorrect information. As you can see in the photo, the shorter slide on the left was in the carb. The 2.5 slide is the one on the right. Both longer & the recommended slide for a 94 Wombat with a 24mm carb. Victor

[Bullfrog]

. . . and the following statement appears to be "spot on":

"It also appears that the 2.0 slide was not traveling all the way down,"

There was some sort of problem preventing the 2.0 slide from "bottoming" - it wasn't getting down to the proper closed throttle position, which resulted in high idle speed.

My interest in posting on this topic is to correct the comment that the 2.0 slide was "leaner" than the 2.5 slide. If folks go forward with that mistaken thought in mind, their future jetting endeavors will even more mysteriously difficult.

Long distance diagnosis does indeed have its issues. Glad to hear the correct conclusion has been arrived at - the 2.0 slide had some sort of mechanical issue preventing proper operation.

Ed

[matt glascock]

Is the slide on the left of the picture a correct valve for that carburetor in general?

[olddogs]

Just a quick reminder for anyone doing carb swaps.
One thing that can sometimes be overlooked when doing carb or slide swapping is to make sure the throttle cable is adjusted correctly. Their are dozens of different styles of mikuni carbs in the same millimeter ratings and many parts may be swapped if they are assembled from parts. I always make sure I hear a good thunk when the throttle is twisted and quickly released. Make sure you try it at full steering lock in both directions. Just a slight variation in cable length can have you chasing starting and idling problems forever.

[viclioce]

Joe. All I can tell you is the cable was brand new. It appears the return spring inside the top of the slide was binding. But, the slide was also much shorter as shown in the photo.

Ed, thanks for the clarification on the 2.0 vs the 2.5 slides. I should have separated the comment by saying because it would not return all the way down, it was running too lean & idling too high.

In any event, putting the 2.5 slide specified for the VM24 SH-83B carb with a different spring seems to have cleared up the issues. Victor

[Bullfrog]

No it was not running too lean because of the 2.0 slide. It was idling wayeee too fast because the slide was not bottoming i.e. it was at a partial throttle setting of (say) 1/8th or 1/4 throttle when it was supposed to be at zero (idle) throttle. Not lean, -- advanced throttle.
Ed

[eddiewombat]

Question:
I have an early Wombat, #17 off the line. I was told the early carbs were garbage and Hodaka changed the carbs out once they figured out the problem. Anybody know anything about that?

[dirty_rat]

If you look at the carb on the left, in the bottom of the venturi (below where the slide would go) you can see a brass extension of the needle jet assembly. If it is sticking up like that one, it should be one of the good ones. The carb on the right you can't tell, because the slide is in the way of seeing the brass extension. While both of those carbs appear to be 24mm, they are different models (like one from a Wombat and one from a Super Rat of other brand bike).

[ncwLoren]

I also have an early Wombat with the early style carb. I've been tinkering with it off and on for years and have never been able to get it to run the way I would like. I was told about the "boat anchor carb" issue and was lucky enough to find a "good" carb on ebay. I assumed once I changed carbs the thing would run great. It did not. I followed all the jetting procedures in the Wombat manual and it runs, just not well. So I pulled out the boat anchor and set it back to stock as per the manual and put it on the bike and preliminary indications are that the bike runs much better. So yes it is a known issue and the Wombat manual gives the serial #s that are affected. In my case I'm kind of perplexed but am not going to argue with positive results.

[danielmp30]

Hi All,

I'm new to the forum and also a first time owner of a Hodaka Road Toad (99). I'm wondering if you could help be identify an issue I'm having with my carb. When I leave the valve open on the bottom of the gas tank, I'm getting a leak out of the bottom of the carb. It appears that there's some type of zerk fitting on the bottom that's broken. It's located right next to the drain plug. Any ideas what this part might be? I'm trying to find a replacement for it, but can't find a good schematic that shows the bottom of the carb.

Thanks in advance for the help.

Dan

[Dale]

That appears to be just the carb bowl overflow. There is usually a short length of tubing to drain over the back side of the motor. The issue is most likely from the float valve and seat not sealing and shutting off the gas flow when the floats put pressure on it. Could also be a leaking float but less likely.
The float valve might just need a good cleaning. Replacements are also available.

[MTrat]

I have one of the 'boat anchor' carbs. What parts need to be replaced to make it work right?

[Bullfrog]

Methinks you may be missing the point about the boat anchor/paper weight carb. NO one has found the proper mix of parts to make it run right (not even Harry Taylor).

Ed

[viclioce]

Well I got my missing pieces installed . She’s starting right up but won’t stay running.

The float arms are set too high now. May be keeping the flow of fuel down. May need to clean the pilot jet one more time as well ......

More to come... Victor

[viclioce]

She runs! Runs like a deer from a hunter!!!

I got her to run thru all 5 gears. May need to drop the needle clip to position #4 to get the mid-throttle where I want her.

But I finally rode my CW, around the neighborhood! Yippie!!!

Now on to the clutch on the Ace B for another go round! And a great big thanks to Rick Mott for the CW repro kill switch he sent me! Works like a charm!