First ride and "rich" experience

Discussion in 'General Questions' started by emdude, Feb 16, 2009.

  1. emdude

    emdude Member

    Finally got my motorized huffy cruiser on the road yesterday for the first time. It fired right up and once I adjusted the idle speed screw would idle fine. But WOW did my engine ever run FAT right out of the box. This thing would never stop four-stroking at all!!!. It's set up to run real rich from what I can tell. This stands to reason since I would imagine the makers don't want a seized piston within the first few miles of use. I decided to ride a bit even under these conditions and then go back home and have a look at what could be done about this.

    I need to add that I live at altitude, 1600 feet to be specific and that of course doesn't help.

    I also had some leaks from the carb, one was due to a loose float needle seat and the other from a not all to good seal of the float bowl. Got those items taken care of.

    Another thing that indicated really rich mixture was the old "shut off the fuel and see what happens" trick. So I shut off the fuel supply on a long straight away and sure enough power picked up for a brief moment just before the engine shut off. This increased my confidence in assuming the engine was running way too rich.

    So in examining the supper richness of the engines running I tried the following:

    First I ran it with out the air cleaner just to see if this made any difference. Nothing of note here, seems this flows enough.

    After that I lowered the jet needle to its lowest position and lowered the float level. The float level seems to be suspiciously high. This made a major improvement. Most of the four stroking was now gone. I could get up most hills in my area with out having to help it along by pedaling.

    Of course it still four stroked at higher RPMs which I would sort of expect. Most small engines like this do because it reaches a point at which the exhaust is the limiting factor. It just won't let enough out anymore. Actually this can be caused by pretty much anything, not enough getting out, not enough getting in, or even any not ideal timing event including transfer ports. I did think it was the exhaust though in my case.

    Then I removed the end of the exhaust. And that made all the difference!!!. Plenty of noise of course and no more four stroking at all. It really picked up and went at all RPMs. There's a lot being lost in the EPA exhaust that came with my engine.

    I'm going to work on getting the mixture as right as I can get it and if I find anything noteworthy will report.

    In my first post I had described how I had a close look at my engine before ever installing it. I had found that on my engine the cylinder base gasket was not cut all that well and was quite substantially covering the transfer ports. I had decided too leave it alone, which I now regret. This could be quite a limitation after all. I may have to take the engine out get this cleaned up just to be sure I'm not taking a hit here.


    I went home for lunch today, after writing the above earlier this morning and tried to start the bike. It's fairly cold here so I set the choke. No deal, would not run. Started right away with the choke turned fully off. Another indication of a rich mixture.


    Last edited by a moderator: Dec 15, 2015

  2. Mountainman

    Mountainman Active Member

    hey emdude

    sounds like fun you are having on that motor bike THING
    you seem to have read up and done your homework
    you are breaking it in a little -- right ?

    enjoy the ride on that THING
  3. emdude

    emdude Member

    >sounds like fun you are having on that motor bike THING
    >you seem to have read up and done your homework

    Actually it's not so much that I read up on anything but more memories of when I was growing up in Germany where 50 cc mopeds was all we had. I remember going through all these things trying to squeeze every bit of performance out of those government strangled little engines.

    >you are breaking it in a little -- right ?

    Well yes. But my theory on this follows the idea of lots of thermal stress in the sense of heating it up and letting it cool down often in addition to lots of varying RPMs.

    >enjoy the ride on that THING

    Yeah, sorry about that THING bit. But I'll tell ya, this is a lot more fun than any moped I ever had!!!


  4. oldsalt

    oldsalt New Member


    I'm getting the idea that the needle is never completely withdrawn from the main jet, even at WOT, regardles of which groove the c-clip is on. If so this is the first slide carb I have ever heard of that used a a needle to change anything but the 'midrange'. I suppose I'll find out when the carb is torn down. I too have a new motor [my first] that is incapable, in its present state of tune, of doing anything but 4-stroke. Very rich at all throttle openings. The newly offered "EPA" muffler came with my motor. I'm thinking the first move, before float heigth and needle height adjustments are undertaken, would be to open up the exhaust track a bit, then mess around with the carb. Does that make sence?
  5. emdude

    emdude Member

    Well, just last night after work I took my MB out for a spin around the block. Ran ok but still some of four stroking. Basically the engine is still running too rich even after what changes I made in my first post.

    I thought of the muffler and again went home and took the end off. And that really did it. It's such a huge improvement. I can now make it up any hill in my area pretty comfortably, and there are MANY of those where I live. and the only four stroking I do get is at top speed rpms. And that's ok because that can be out later.

    On my EPA exhaust, on which the fine paint burned off in the first minute of running the engine BTW, the pipe that exits to the outside goes INTO the exhaust by quite a few inches. I have not examined this all to closely but in any case the internal pipe is going to be cut today on a band saw a my work. I'll let you all know if this made any difference.


  6. oldsalt

    oldsalt New Member


    Believe that'll be my first move; get rid of some of the restriction in that limp-wrested EPA muffler. There's no hope of ever getting the carb to work with an exhaust system incapable of resonable scavaging. THEN work on the needle and float level.
  7. emdude

    emdude Member

    restrictive exhaust

    Well, yesterday I cut off most of the internal pipe in my EPA muffler. A good 5 or 6 inches worth. It did make a difference. The exhaust is definitely louder but not enough to cause much concern that I'll be annoying the neighbors. The engine does run stronger with less four stroking but is still too rich.

    Bu I'm basing that on my distant past experience with the little moped engines I messed with mentioned in earlier posts. I recall that the best performance was obtained, with any given set of otherwise given conditions such a exhaust being what it was when the carb was leaned out to the point in which the engine NEVER four stroked und full throttle. The engine would produce good power and simply spin up to maximum RPM at which they could just do no more. Top end four stroking was completely gone is this case.

    Short of removing or modifying internal baffles in the exhaust this is about what can be done and from what I can tell if the carb could be leaned out just a bit more the engine would be running quite good. Although I do think there is quite a bit of power to be had if one were to try and max it out.

    So the next step will be an attack on the main jet. I've seen that some on this forum have soldered it shut, so to speak, and then re-drilled it for a smaller diameter. This is I'm sure ideal, short of getting a smaller diameter main jet.

    But in my case I think I'll start with the old "small wire in the main jet" trick just to see if this can get me any closer. If it does I can make a more educated guess on just what size to drill if I do solder the jet closed.

    One thing that does NOT help in my case is that I do have some some small amount of air leakage between the carb and the intake manifold, engine stalls when carb cleaner is sprayed near the area. So tonight or tomorrow I'm going to fill in the slots on the carb with silicon. That should take care of that problem and give a better platform for getting the carb set up right.
  8. srdavo

    srdavo Active Member

    you can put an o-ring in the carb, where it meets the manifold.'s a good idea to replace the manifold gasket.
    once you stop all the air leaks.... you should see a great improvement.
  9. emdude

    emdude Member

    Yeah, I was thinking of the O-ring thing also. And I just so happen to have an O-ring kit with plenty of selection in my garage. My concern with that is just that I would want to see a real good tight fit because I'd hate to see the O-ring wander down the intake. Maybe I could glue it in place with some silicon?

    But I'll examine that option and If I come up with something that works I'll post.

  10. wildemere

    wildemere Member

    Don't wire the main jet, file 2.5mm of the bottom of the slide duplicating the 1mm cutaway. Measure it with a vernier first.

    Incidentally the cutaway's size tunes off idle response, a 1.5mm cut will be leaner up to around half throttle.

    Each notch in the needle is 1mm so you will gain 2.5 notches of leanness with this method I developed.

    A side benefit is you can now have a carb with perfect tune at 2.5 mm before the slide stops so your full throttle is position now earlier in the slide travel and so there is 2.5mm of extra richness for high load conditions.

    Or you can set it perfect at "full throttle" and it will be a tad leaner everywhere else.

    I use 0.5mm washers on the needle then plug readings to get close then a thermometer aimed at the head near the plug to set full throttle tune.

    180 degrees celcius seems right when its 20 ambient more is lean and cooler is rich.

    A pyro in the exhaust would be better though.
  11. emdude

    emdude Member

    Wow, thanks, that's an idea!!!

    I'll have to look at my slide and see if I think I can safely take off 2.5 mm.

    So I assume you had issues with an overly rich running engine as well?
  12. oldsalt

    oldsalt New Member

    Regarding the leak between the manifold and the carb: I noticed, when I was assembling, that the end of the manifold that inserts into the carb was not long enough to completely seat in the bottom of the recess in the carb. Also it was not cut squarely on the end. Of course the only other thing that could be wrong was also evident; The end was out of round. When I was correcting these things it occured to me that some young builders might not realize that the carb did not seat all the way and resulted in an air leak. I'm going to spray some carb cleaner on mine to see if, in fact, there is no leak there. Then I'm going to chop the muffler tube and go for a ride.
  13. oldsalt

    oldsalt New Member


    I'm not too quick on the uptake. Do you mean to remove 2.5mm [approx. .100"] from the cutaway and to do so at the same angle as the current 1mm cutaway. Or remove the 2.5mm at a new angle slanting rearward to the centerline of the slide? That's how we did it, to change the off idle transition, back when Indy cars had skinny tires. Seems like you have done a lot of work on this subject. Incidently, I just now pulled out my slide and found that the needle is on it's lowest notch but the mixture is fat all the way through! Do you have an opinion on what muffler I should be useing, or just alter the existing EPA unit?
  14. emdude

    emdude Member

    WOW I, wired!!!!

    OK, I'm the one that started the thread "first ride and rich experience.

    OK so I completely removed the inner tube from my muffler. That helped a little but not much.
    I posted that I was sure the engine was running way too rich. See prior posts. I also said I'd the wire in the main jet thing just see if this would have much effect on leaning things out a bit.

    And while I do have to still give some consideration to the idea that filing the bottom of the slide may be a better solution, after wrenching around all day on numerous things, including a broken rear fender mount on the huffy, I decided to end the day with one last experiment:

    I did as threatened and took some very thin wire, I think it's AWG 30, the stuff they use for wire wrap proto boards and inserted it in the main jet bore. I wraped the rest around outside of the main jet a few tomes a carefully reinstalled the main jet making sure the wire was secure when the main jet was screwed in.

    WOW that did it. It leaned the carb out just about perfect Great response, good power up hills and NO MORE FOUR STROKING!!!! The bike now really zips along nicely.

    Well, it does still four stroke a bit but only at pretty high RPMs that I have no intention of sustaining for any length of time with the engine as fresh as it is. The difference is HUGE. The engine now really runs the way I expect a 2 stroke to run.

    The bottom line is that the richness in my case does require a more permanent solution than the wire in the main jet. Be it a different main jet, a cut slide or a soldered and re-drilled main jet. But the wire got me to I know for sure.

    Just thought I share this.
  15. oldsalt

    oldsalt New Member

    The bit of 4-stroke at elevated RPM sounds O.K. to me. For starters I'll cook the EPA muffler then solder up the jet and drill it slightly smaller. If the mid range becomes a problem the slide can be cut and/or the needle sanded. You guys have really saved me a lot of time trying to figure it out on my own.
  16. oldsalt

    oldsalt New Member

    This afternoon the cap on the EPA muffler was pulled for a look inside. What a mess. Took a acet. torch and blew out a 1/2" wide X 3" long 'slot' down the side of the input tube. Stock it is plugged off at its discharge end and is drilled with a number of small holes. Then cut off the output tube so that only 1-1/2" is protruding on the inside. Put the cap back on and mounted the muffler on the engine and went for a little ride. What a difference! She pulls a lot more strongly all the way up to max R's. At that point it begins to 4-stroke. If I roll off the throttle a hair the engine gets back to businss with proper 2-stroking. Really, I can now live with it! But it can be improved.

    Got to bear in mind that the test ride was in very dense cold air and that the gas/oil fuel mix being used is the really rich blend used for break-in. It's almost sure to 4-stroke even more in thinner air and useing thinner fuel. The stock jet will accept a .024" diameter drill, but won't accept a .0265" drill. I don't have a .025" drill which is probably near the stock size. After some more riding in warmer weather and some plug readings I'll probably have to do something to lean out the mixture a tad on the top end. But there's a LOT to be said for running a fat mixture in a 2-stroke at the top end.
  17. emdude

    emdude Member

    I'd like to know more detail on what you found inside the epa exhaust.

    >Took a acet. torch and blew out a 1/2" wide X 3" long 'slot' down the side of >the input tube.
    >Stock it is plugged off at its discharge end and is drilled with a number of small >holes.

    By input tube do you mean the "header" as it goes into the larger part of the exhaust/muffler?.

    As I had posted previously I have completely removed the the INNER part of the exit tube on mine but all the internal baffles are still there and intact. And with the leaning out of the carb I've done it runs pretty good. It spins up fine with reasonable power and ends at some higher RPM with moderate four stroking. Which is about what I would expect. What is interesting is that it will occasionally break out the top end four stroking, revert to two stroking and you can feel a noticable "pull". It really seems like there is quite a bit left to be had in this little engine if it were tuned perfectly.

    I now really feel like kicking myself because:

    In one my early posts I had described what I had found when I examined my engine shortly after getting it before I had even begun to install it in my bike. I had pulled the top end just to see what this all looked like and found that the base gasket between cylinder and crank case was cut quite poorly. It was blocking a substantial amount of the transfer ports. And if a chain is only as strong as it's weakest link, well this could be the weakest link at some point. I reasoned that this would wear off over time since there was already evidence of this from the test run they had done in China when they made the engine. Now I wonder just how long this might really take. Pure bone headedness on my part for not considering that anything that does wear off has to be "eaten" by the engine.

    I suppose I could pull the top end with the engine in the bike and check just to be sure.
  18. oldsalt

    oldsalt New Member


    Yes, by 'header' I mean the exhaust pipe. The pipe from the exhaust port travels all the way to the bottom of the muffler shell. Almost to the bottom where it is capped off. The only way any exhaust gas can escape from it is through a number of approx. 1/4" dia. holes drilled in the tube near its lower portion. Really big burrs are evident due to the use of a rather dull drill. There's a tight fitting baffle at about the middle of the muffler shell. The baffle has a hole to accept the long out-put tube which begins near the top end of the muffler shell. [The tube that we both cut off]. The baffle also has a couple of holes to allow the exhaust gases, that exit the 1/4" holes, to travel upward to the open end of the out-put tube. What I did with the oxy/acet. torch was to blow out the side of the lower end of the input pipe. A slot, in the area of the existing 1/4" holes, was cut about 1/2" wide and about 3" up the tube. Was able to do this without blueing the chrome. Would have used a milling machine to reach down there but it would have neen difficult to hold in a vice. This provided an opening many times bigger in area than the 1/4" holes. As said before, the out-put pipe was cut off to a length that positioned its input end to be at the level of the 1/2" X 3" slot in the in-put tube. The noise was only slightly increased by these modifications. I regreted not taking some sound level readings on the "before modified" muffler. I'll check what it is on the modified muffler and post that information. But it is NOT loud in any sence of the word. Just added a 'put-put' to the nornal hummm; no harsh sounds.

    Regarding the transfer ports being obscured by a sloppy gasket: I am going to pull the head off my engine and most probably mill off a little. Sure don't know how much yet, but I'll be in a position to see what my base gasket looks like. As with you, I don't like the idea of my little engine slowly chewing up gasket material and spitting it out.
  19. emdude

    emdude Member

    Hey old salt:

    For what it's worth:

    Yesterday after work I pulled the head off my engine because I had the slight suspicion that it may have been leaking just bit. But also because I just had to check on those transfer ports. In the process I took another close look at the ports with the piston in TDC and BDC. It looks as though with the piston in BDC the transfer ports are 90 % open but the top of the piston still covers a tiny bit of the bottom of the port. I would think based on this that a small spacer under the cylinder would not make much difference, and may even improve things.


    Looking into the intake with the piston at TDC I did notice that the piston skirt was still visible by over 1 mm. In other words the piston skirt does not fully get out of the way of the intake at TDC. But what's really scary is that with the piston at BDC and looking into the intake the UPPER piston ring is clearly visible. This seems almost dangerously close to being able to get leakage above the piston. After noticing this I'm coming to the conclusion that a small spacer may in fact be a benefit. I'd prefer to NOT be able to see the upper ring at the intake at all with the piston at BDC.

    Also a small spacer under the cylinder would move the relative position of the piston skirt up and closer to fully out of the way.

    So over all, short of the loss in compression I think it would be a wash or a benefit. I just may have to try it.

    I've run only about one full tank of gas through mine so the base gasket on the cylinder had not yet glued itself to the case and I was able to get the cylinder off quite easily.

    I did leave the piston in the cylinder because during my first examination of the engine I recalled having a hard time getting the rings back in. I don't recall this being that difficult on the engines I worked on as a kid. I just removed the wrist pin, AND DIDN'T LOOSE THE CLIP!!!, and pulled the barrel off. I suppose that this might present a problem if the engine is mounted higher in a bike frame than mine. You'd have to pull the studs also.

    I looked at the gasket around the the transfer ports and all of the material I had noticed during my first pre-installed examination was GONE!!!. I know it was there, **** I should have taken a picture. The gasket had been eaten away right down to the border of the the outline of the transfer ports on the cylinder.

    I could see that if this where the case for all these engines it would be one of the reasons for the claim that they "break in" within the first hour or so of operation.

    So I put it all together again. And had to really juggle things around a bit to make sure the piston didn't hit the head or the gasket. As I said on my engine this is all a bit sloppy. I removed the magneto side cover, pulled the clutch and turned the crank through TDC with a wrench with the head mounted fairly loose and still adjustable. You have to get it all lined up just perfect or the piston will hit the head or gasket. You can feel it for sure. Makes me wonder what might happen after things heat up?

    With that said, you can probably spare yourself the trouble of pulling the barrel to check the gasket around the transfer ports.

    I have to say that I'm a bit suspicious of that head gasket they use. I mean now there are 2 junctions that potentially can leak instead of only one if the head were mounted directly. I'm going to have to really examine this some time and see if the head gasket is in fact needed for clearance.
  20. oldsalt

    oldsalt New Member


    I'm going to pull the barrel off my engine before doing anymore riding. It's snowing anyway. If my engine is comparable to yours, in regard to the piston not clearing ports and etc., a spacer will be made. As the machine tools are available the head will also be cut to retain the orginal compression [or a little more].

    Somehow I'm not surprised by your findings an won't be surprised by what is found in my engine.

    You mentioned break in. The book says 500km. That has to be bogus! There's nothing to 'break in' except the bore and it has a plated cylinder! It isn't a cast bore. Sure, as a precaution a little time should be put on the motor to make sure some little high spot on the piston gets friendly with the bore before the engine is operated at full song. But certainly not 500km, that's pure drivel. I will considered my engine ready for the heat of battle when the 4-stroking is cured and the engine has an hour on it.