Okay here goes. I have a 1977 03 Wombat completely stock . I have cleaned the carb over and over again. I have my own dip tank and at this point in time you could eat off of this carb. She is clean. I set the idle and then set the air mixture screw at 1 1/2 as per the manual. Spark plug gap is set and it starts on the first kick.
Here is the problem. It does not run clean at my higher RPM's. When you are riding it you constantly have to feather the throttle and adjust to get it to runs smooth. It kind of cuts out. Low RPM and just putting around, the thing runs great. When I am hammering on it and trying to have the real good fun, it just is not running clean. I have tried to adjust the carb and went to lean and broke a skirt off the piston once. Paul hooked me up with a new one.
What am I missing here? The only thing that I can see that may be wrong, but i didn't think it would be it, was my needle coming off of the slide has a rough spot mid shaft. I polished it and it is pretty smooth. But like I said mid shaft. And very small imperfection.
Any help is appreciated. Thanks.
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Forum Admin - 10/16/07 at 5:05pm
If you are loading up at the " top " do you mean 3/4 to full throttle ?? Sometimes it is very hard to tell the difference from the bike gulping for more fuel or choking from having to much fuel.
When you say you are putting around it runs great this would be the pilot jet ( up to 1/4 turn of throttle) then ( 1/4 turn to 3/4 turns throttle is the needle jet and the jet needle. So it sounds like to me that you are saying that the pilot jey and the neddle jet plus the needle are fine. We need to fix the 3/4 to full throttle area. This most likely will be a main jet issue. Have you decarbonized the baffle in your exhaust pipe ??
I hope this may help.
Thank you
Paul
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Bullfrog - 10/16/07 at 7:00pm
There are a couple/three things Paul didn't mention, which I feel I must.
1. Checking jetting with the Mikuni carburetor depends on throttle position , not engine RPM. So you may be thinking, "But I only hit top RPM at full throttle." Interesting thought - but not true. In the lower gears, 1/2 throttle can produce engine revs into the white sound region. On a slight downhill with a bit of a tailwind, you can hold 50mph at 1/8th throttle (firmly in the pilot jet "range" of tuning). So try to adjust your thinking to: "What throttle position am I holding when the engine runs bad?" OK?
2. VERY roughly
- the pilot jet and pilot air screw control the air/fuel ratio from 0 to 1/4+ throttle
- the slide cut-away controls mixture from 1/4(-) to 1/2+ throttle
- the needle and needle jet are in control from 1/2(-) to 3/4+ throttle
- and the main jet controls from about 3/4 to full throttle
So descriptions of how the engine runs when the throttle is held at each "1/8" and/or "1/4" position will really help diagnose the problem. (0, 1/8, 1/4, 3/8, 1/2 etc.)
3. Breaking piston skirts generally doesn't happen due to jetting . . . or at least the massive seizure which caused the skirt to break gets mentioned. If the engine did NOT seize, but broke the skirt - it is quite likely that the piston and the cylinder bore were simply so very worn out that something had to give. Mechanics sometimes joke about pistons which are traveling as far sideways in the bore as they do up and down when things get really worn.
Finally, if you can SEE the worn spot on your needle at 1/2 to 5/8 throttle when you look inside the carb throat - it is probably not causing your problem. (When you can see the worn spot - it is not down in the outlet end of the needle jet doing any metering.) BUT, a needle that is not worn and/or polished is highly recommended.
It sort of sounds like maybe, possibly, it might be, that your main jet is too large. But I'd really, really like to know what size main jet is in there before recommending leaning out.
NOTE: A plugged or partially plugged exhaust system will adversely affect engine operation more at higher RPMs. So that would be a very good thing to check BEFORE messing about with jetting. Also - timing properly set?
Ed
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Forum Admin - 10/16/07 at 7:41pm
Yeh what he said
Honestly having Ed with all the Hodaka guys to offer suggestions, help or advise is unbelievably great. Ed was PABATCO's Service Manager from 1975 through 1978 ?( Ed is this correct or close to ? ). But the point is to have Ed answer the technical questions for all of us is a luxury none of us should just accept as normal.What I mean is where can you actually post on the internet a technical question and have one of the original " real" service managers of a specific brand offer technical assistance ? If you are on Phil's Yahoo site or here and have a problem Ed is there.
From all of us Hodakafiles thanks Ed !
Every one of us appreciate all you do to help keep Hodaka's going into the future. I am proud as hell that you are Chris's and my teammate at the ISDTR too.
Paul
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FastMag - 10/16/07 at 10:49pm
I have not decarbonized the baffle in my exhaust pipe. Is it just a pull out and wire brush it out?
The bike did sit for a number of years. The worn spot in the needle appears to be at the height of with the throttle close it would be right where it was sitting in the jet.
The not so clear running is at 3/4 throttle to full throttle.
The exhaust note does change at 3/4 throttle to a duller sound (not as crisp as a two stroker should be). I will check the manual to see if they also have decarbonizing instructions.
Thanks.
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Forum Admin - 10/17/07 at 10:13am
John the clip on the needle is a good idea but if he is having the trouble from 3/4 throttle to wide open this is the main jet range. The needle jet and jet needle control the area of the throttle from 1/4 turns to 3/4 turns.
It is extremely hard to tell where you are when turning the throttle while riding. Jim Gentry from PABATCO had given me a great idea many years ago. He suggested putting a thin strip of white tape on my throttle housing and then three thin strips of white tape on my throttle grip (one at 1/4 throttle, 1/2 throttle, 3/4 throttle ) so that I could look down and see exactly where the throttle is at.
Believe it or not before I did this when I thought I was at 3/4 throttle I was not even close. Having trouble when the throttle is wide open is easy as you cannot turn the throttle any further.
How I personally decarbonize the baffles is to take the baffle out of the pipe. For the 03 Wombat this is a two piece baffle ( inner and outer). I take them outside to my gravel driveway and while wearing safety glasses proceed to cook them one at a time with a propane torch. I turn them red hot and keep heating while they are smoking like crazy. Once they stop smoking I let them cool and with a wire brush the carbon falls off real easy. For the inside of the baffles I either tap them on a block of wood or reach in with a long thin stiff brush I have here.
The stock size for your main jet on the 03 Wombat is a # 180. Is this what is in the bike now ?
Are you still running the bike with the oil injection hooked up ?
What are you using for the air filter element ?
Is your element a two piece element with one part wrapping around the screen and the other as a cap to protect from dirt and such getting by the drilled with holes inner airbox cover ?
Thanks
Paul
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FastMag - 10/18/07 at 12:39am
I took the muffler apart and got the baffle out. I wire brushed the living daylights out of it and it cleaned up pretty well. I did get all three parts apart and the little star thing out of the bottom of the baffle. I got it all back together and it did run better but still stumbles at the higher RPM, maybe the last 1/8 throttle now.
Tomorrow night I will pull the carb and read the Jet size. The needle is in the middle position. When I got the bike it only had 1400 miles on it and it was a camp bike. I am 2nd owner. I now the first owner did not do any changeing of jets or anything to it, he bought and rode it until it fell off the trailer and then he put it away and never touched it again.
The plug looks a little rich and dark but it has had very short run time on it, mabye 20 miles since putting it in.
I am at 200ft elevation if that makes a difference on settings.
I will also redo the float level to make that is not doing it.
I am still running the oil injection system and it does work. Oil is flowing to all ports. I am using Valvoline Multipurpose 2 cycle engine oil.
I am using a two piece airfilter. I did make it out of some airfilter foam from the local honda shop. it does wrap all the way around the cage and I cut out a lid filter. It was a UNI filter material.
I will know more tomorrow evening.
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Forum Admin - 10/18/07 at 6:25am
Fastmag thanks for the update this is good information.
The star thing you refer to is actually your spark arrester. I thought it was hokie but Harry told me this was a simple but great working deal.
How was the inside of what I am calling the outer baffle ?
Was the previous owner also riding the bike at your elevation ( 200 feet) ?
Double checking the float level for sure cannot hurt but my personal feeling is that this is not your trouble.
It sounds like you did good with the air element but what is the thickness of the material and also the color ?
Now I may have Ed jump in and hope he does to add to this but with the oil injection system the oil pump and throttle are set to open together when you twist your throttle. Saying that this gives you a 20:1 fuel oil ratio. I am unfamiliar with how to accurately reduce the amount of oil with this system to better give a 40:1 ratio with modern day oils which would be optimum in my opinion again. This is the main reason why I have personally disconnected the oil injection system on all my rider Hodaka's that had the system in place. This was done on the 250 E.D. that BoJo will be riding at the ISDTR. I could just not get the bikes to run clean with the oil injection in palce but that is not to say that someone else can make it work.
For all other models that had the oil injection except the 03 Wombat this is easy just block off the banjo bolt with a solid bolt to stop the flow of oil being introduced at the intake manifold. But the 03 Wombat has two oil lines. One going to the intake manifold and one feeding oil the the left main bearing. So to disconnect the oil injection for the 03 Wombat the motor needs to be disassembled and a small hole needs to be drilled in the left inside case down into the the left main bearing. Oil from the premix then will lubricate the bearing as on all the other Hodaka models.
I hope this makes sese it is real early here and I am real tired. Not enough coffee yet.
Good luck with your project I hope this all may have helped.
Paul
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FastMag - 10/19/07 at 2:43am
I have a new issue that has cropped up during this. I have seemed to have lost all spark now, Kinda making it hard for testing at this point.
This is the good fun of playing on 30 year old bikes. You are always chasing something.
At first I was all into to keeping it as stock as possible, but now I am looking at making it as fun as possible.
Can I un-hook the intake oil injection, leaving the main bearing hooked up to get injected and do premix to get the right combo? Whithout drilling the hole. Wouldn't the second line take care of the hole? Ed?
I am going to spend the next few evenings finding out why I lost spark. I know I will need a new 03 kill swith at this point. I kind of destroyed my old one taking it apart. Lesson learned.
My spark plug gap was littel to small, I discovered. 18 instead of 24-27. That is fixed.
The Uni filter foam I bought was light green. ?? kind of thin.
I will keep everyone up to tabs on te fix on this.
My goal is, I have a friend that just got his restored 1982 Husky 500 back together and we are to go riding. I ride year round on street and dirt bikes and have since I was 3 (36 now) and he hasn't ridden for 20 years. So I am tinking that a good 125 and skill will keep up with a 500 Husky noob in the dirt.
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Bullfrog - 10/19/07 at 3:42am
Clean the points - sounds like you've used up the kill switch, so it must be disconnected (which is good when chasing lost spark).
I don't think I'd recommend removing one of the two oil delivery lines. The metering pump is a positive displacement unit, so it is going to put out the same amount of oil whether there are two lines connected or one.
While you are working on the spark issue, check the oil injection pump settings/actuation.
1. Make sure the mark on the pump actuation cam/pulley aligns with the mark on the pump body when the throttle is OFF. Bend the little tang as necessary.
2. Adjust the throttle and oil pump cables as needed to make sure the oil pump actuation cable and the throttle cable come tight at precisely the same time - so the throttle slide and the pump cam/pulley are precisely synchronized.
If I remember correctly, the current thinking on spark plug gap calls for .018" . . . is that right Paul?
If your Uni-foam is 5/8" thick . . . you'll be fine.
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