Larger Carb

[PoolGuy]

I bought a 73 Wombat 94A on ebay about a month ago. Somewhere in its history a carb from a model 95 Combat Wombat was put on, along with a reed valve. I cannot get it to start easily or idle. I figure increasing the pilot jet will help. Also, since it has a reed valve, does it still need the heat block between the carb and the cylinder? Thanks.

[racerclam]

How many turns out is the air screw out for it to idle ? If it need to be almost all the way in then yes a larger pilot jet is needed. The heat block , if the reeds was from the enduro cross kit the carb fits without.

Rich

[PoolGuy]

Well that's the thing. Can't get it to idle no matter how many turns of the air screw. Takes me maybe 40 kicks to get it to start, Runs fine as long as I keep the throttle high enough. Plug looked good after I ran it for 5 minutes. Won't start easily and won't idle. Frustrating

[olddogs]

I would check a couple things.
Is the current pilot jet plugged. Hold it up to a light. You should be able to see through it.
Check the compression. Worn rings will make it hard to start.
Old gas. The cheap gas they sell now will go stale in 6 months. I have had it go bad just sitting over the winter.

[Scribbler]

I would second olddogs suggestion of clogged pilot jet. A major cause of no idle. I had a Honda Spree 50cc that would not idle. The pilot jet was clogged. It was a very tiny jet. I pulled a bristle out of a fine brass wire brush and carefully cleaned it out. Had a piece of carbon or something in it. Idled great after that. I had soaked the carb and sprayed it but it took mechanical cleaning of the jet to clear it out. You need to see a pinprick of light through it.

[PoolGuy]

Pilot jet all nice and clean. I will check compression. I was reading about the reed valve setup. It was suggested that the reed inhibits the suction into the cylinder during start up, so the pilot jet needs to be enlarged. I also think that, since the heat block increases the distance from cylinder to carb, that will also impact the size of the pilot jet needed. Going to remove heat block, increase jet size and check the compression. Lots of funny things on this Wombat. The previous owner was trying to turn it onto a Super Rat. He painted the frame orange, installed a Super Rat air filter, took off all the extra hardware and lights and wiring. I find something unusual every time I work on it. Fun project(mostly).
Thanks.

[Dale]

I was wondering about the carb/reed setup and thinking that you are on the right track. I wonder if the piston is correct for the reed setup? When all is right, this bike should start up in one very easy kick. Back to the pilot jet, do not overlook the internal passages of the pilot circuit. They are also very small and plug easily. However, if it was the pilot circuit at fault you would probably find that the bike would start and run as long as the choke is on and then die as soon you release the choke...
Dale

[PoolGuy]

Thanks for info on pilot jet and pilot circuit. I cleaned out the carb body and shot air through every passage. Jets are clean as can be, took it all apart and inspected. It absolutely won't start or run if I come anywhere near the choke. Guess I'll just wait for the new pilot jet.
Tom

[Bullfrog]

Things just aren't sounding right. I think it might be time to remove the carb and the reed cage and then take a peek into the engine.

While you have the reed cage out, check to see that the reeds are coming to rest nicely on cage. They need to "seal" - not a true airtight seal, just rest against the cage nice and flat -- no curl or "lift up" when at rest.

Now for the engine, is the intake side of the piston "solid"? Or does it have holes in the skirt on the intake side. It must have holes to work properly with the reed. How about the top of the intake port of the cylinder? Are there holes/large grooves which allow fuel to flow up where the "ceiling" of the original intake port used to be? Those ports must be there too.

Can you tell that I'm starting to wonder whether or not we might have a situation where no porting was done, and the piston was not modified . . . but a reed valve assembly was bolted on. If that's the case, it just isn't going to work.

Ed

[PoolGuy]

I'm getting very suspicious of the reed/cylinder relationship. I increased the pilot jet size and got a small improvement in starting/running. But very inconsistent. After I get it started it will die without my help. Pretty soon I can't start it at all. I don't think I mentioned it, but the carb is from a Combat, so I believe it is larger than for my Model 94A Wombat. So I've got a bigger carb, a reed valve and it's unknown if the cylinder was ported correctly for the reed. I'm going to look at the reed next. On the bright side, I just bought another Wombat, so I can swap out that carb and manifold if I need to. Not ready to look at the cylinder yet, a bit above my skills.
Thanks,
Tom

[PoolGuy]

Finally got back to the bike armed with all the info and parts I could find. I pulled the flywheel to change the points and found the crank seal was no longer in place and everything was gassy and oily around the points. Put in a new seal and points. Removed the reed valve guts. Brought the pilot and main jets back to original sizes. Oh, had trouble finding the correct timing mark on the case because it was so scratched up, but took my time with a magnifying glass and finally got it right. VVRRROOOM! Won't idle but the fuel filter may be restricting gas flow, as well as other carb issues. But hey, finally got to ride the thing and go through the gears. Feels good to be on the right track.

For more fun I bought a so-called barn find. 1972 Model 94 with less than 600 miles. Dusty and rusty but started on 2nd kick with gas down the throat. Much more original and correct than the above model 94A.
Guess I'm hooked.

Thanks for all your suggestions.

[Bullfrog]

NOTE: IF the cylinder is properly ported for the reed valve, you WILL NEED richer jetting than was stock in the carb regardless of whether you retain the Model 95 (28mm) or install the Model 94 (24mm) carb. Both the Model 95 and 94 engines were piston port induction. Changing to reed valve induction REQUIRES richer jetting (pilot jet, throttle valve, needle setting and main jet).

While you had the reed valve guts out, did you peer into the engine? Did you see holes in the intake side of the piston? Hmmmm, did you put the reed valve guts back together on the engine? (Reed valves aren't something to be simply bolted on and/or removed on a whim.) Were the reeds resting nice and flat on the reed cage?

Not having the magneto side main seal in place is a very baaaaaaad thing. Your engine really ought to be pressure tested - you can research it here on this web site. Two stroke engines MUST be AIR-TIGHT to run properly.

Ed

[PoolGuy]

Bullfrog, I will look at the piston as I have the intake and reed assembly off at the moment. I'm new at this, but the intake on the cylinder looked stock. Isn't it supposed to be enlarged for a reed installation? The reed guts are were actually rusty and I left them out. I've been running it without the reed guts in at all and re-installed the smaller pilot and main jet. I'm gearing up for a drop-down test, but since I replaced the magneto-side seal, and the points, it has never run better and started more easily. So there has been improvement. Still won't idle, but for it to even start 2 days in a row is a major victory for me.

[Bullfrog]

PoolGuy:

We NEED to know whether or not there are proper reed valve modification holes in the intake side of the piston. Here is how to get educated on what you are looking for

1. Click on "Return to Strictly Hodaka" on the top banner of this very page.
2. Click on "Shop by Schematics" at the top of the page.
3. Scroll down and click on the Model 97 Super Combat
4. Scroll to and click on "Parts List B"

Look at the piston in the diagram. Does your piston have holes like the ones shown in the diagram on the intake side?

Here is another thing to check.

Switch to "Parts List A" (still in the Model 97 Super Combat)
- The cylinder is shown with the intake manifold removed. In the drawing you can not see the "roof" of the intake port of the cylinder . . . but you can get an idea of the next thing we NEED to know. Is the roof of your cylinder's intake port smooth and flat and sloping down? Or not?

Though it is pretty clear that your engine is indeed (as they say) -- messed up. If your engine were properly modified to run with a reed valve . . . and you took the reeds out . . . it would NOT run.

I fear that it is time for you find some "hands on" help/expertise . . . or start reading and educate yourself about two-stroke engines, including piston-port induction and reed valve induction.

Ed

[PoolGuy]

Excellent. I will do all those things. In the meantime, I got it to run after just a few kicks. It will idle if i keep the throttle open just a bit. From what I could tell, the intake port has not been modified and the piston does not have holes, but I will look closer after I check out the Super Combat schematics.
Thanks

[PoolGuy]

Finally pulled the head and cylinder. There was only about 70 lb compression. I guess it makes sense now. Firstly, there have been NO modifications to accommodate a reed valve. But the biggest problem is a broken ring and a beat up piston. From what I have read, low compression will cause hard starting and poor idle, but run Ok once it gets started. Exactly what was happening. I was hoping for just a ring replacement, but now piston and maybe cylinder too. I found a local guy that will look at it for me in December. So putting it to rest for now. I have learned a lot, and am glad to have found the problem. On to my other barn wombat, which starts on the first kick and seems to act normally.