'84 200s not idling well

[webbch]

I recently rebuilt the motor on my 200s (bored cylinder, oversize piston...stock compression ratio, lapped in a new set of valves, etc). It runs great off idle, throttle is very responsive, definitely not lacking in power, but I just can't seem to get a consistent idle. When I set it close to 1400 RPM, it goes between 1000-1600 RPM for awhile and then dies unless I periodically give it some throttle. Here's what I've done thus far (stock OEM carb):
1) New intake-to-carb boot (and o-rings)
2) Verified no leaks by spraying carb cleaner on intake connections while running
3) Verified float level using plastic tubing on overflow port - it's just a little bit (~1/4") below the carb bowl
4) Pilot screw 2-1/4 turns out. I can go about +/- 2 turns from this position before seeing a drastic change in how the engine runs. Pilot screw has the oring, washer and spring on it. In comparison to a brand new screw from my carb kit, the tip is very slightly worn I suppose.
5) #100 main jet, #35 slow jet.
6) Carb has been fully disassembled, soaked in carb cleaner overnight, then all ports and jets blown out with compressed air before re-assembly.
7) Fresh gas in clean fuel tank.
8) Kill switch is firmly held in center position
9) Set timing at 1300 RPM with timing light - right on the F mark at that RPM.

Like I said, rides around great, just won't hold an idle. I haven't messed with the needle clip position. The only other pertinent info I can think of is that I replaced the exhaust crush gasket during the rebuild, but then did remove the header pipe and re-install it w/o replacing the ex. gasket a second time. Cold starting at around 60 deg F only requires about 1/2 choke, and then only for about 10 seconds, maybe less, then I can turn off the choke.

I disassembled the carb a 2nd time just to make doubly sure the slow jet wasn't clogged for some reason. It looked clean, but I'm cleaning the whole carb again while I have it out just to be sure. I'm waiting to receive a #38 slow jet and will try that to see if it helps, but was wondering if there's anything else I've overlooked that could give rise to a poor idle only. Thanks.

The final interesting tidbit is that within about 5-10 sec of me turning the fuel petcock to the off position, the engine RPM starts to go up. It rises steadily to over 4000 RPM when I shut it off because I don't want to over-rev it. It's not a quick rise right before the engine dies due to lack of fuel, but far more gradual, which I thought was odd.

Chad

[barnett468]

if your current screw looks damaged and you have a new screw, why have you not installed it?

have you left the screw in 1/2 - 3/4 turn in from its current position and out 1/2 - 3/4 turns out for a few minutes to see what it did

how much choke is needed to start it?

how cold is it where you start it?



if it has a float bowl drain screw i would do the following:

connect a clear 10" long piece of clear plastic tubing to drain fitting on bottom of carb.

hold open end even with top of carb.

open gas valve on tank.

open drain screw on carb.

the gas will flow into tube.

it should be from, even with the bottom of the main carb body to around 3/16" below that point.

[Iceracer1]

Air screw and/or pilot jet is usually the culprit when the machine doesn't idle right (if the carb is clean clean). You shouldn't need to use choke at 60 deg. It sounds like its running lean.

[barnett468]

3) Verified float level using plastic tubing on overflow port - it's just a little bit (~1/4") below the carb bowl

Cold starting at around 60 deg F only requires about 1/2 choke, and then only for about 10 seconds, maybe less, then I can turn off the choke.Hello webbch;

I was using a very small screen earlier and didn't see the two items above.


The float level might be a bit low.

The fact that your bike starts easily under these conditions suggests the pilot jet is ideal in my experience, providing the bike is stock with no mods, however, since your getting a 38, maybe that will help.

The Honda owners manual actually suggests full choke at that temp. This further suggests that your pilot is not too lean.

The jets sometimes get a thin layer of dried up crud inside that can be hard to detect, The pilot jet can be cleaned fairly easily with a strand of wire from a wire wheel or wire brush etc if necessary.


Starting Procedure for 200s from owners manual.

Normal Air Temperature
59 – 95 deg f

1. Raise the choke lever to half position [B].
2. Open throttle slightly.
3. Pull recoil starter briskly.
4. Immediately after engine starts, push the choke lever down to the half position [B].
5. After a half a minute after the engine stays, push the choke lever down all the way to Fully Open.


Notice that line 1 and 4 say to do the same thing. This is an error in the instructions. Line 2 should say “Raise the choke lever to the full position [A].”.

[wonderboy]

My 200ES wouldn't idle steadily after a carb rebuild. My issue was due to slide wear. The slide is worn (made worse I think by soaking in carb dip) and there is too much clearance between it and the carb bore it slides in. This lets air pass around the slide causing idle issues.

My solution was to have the slide re-coated. It wasn't my original idea, I'd read up on snowmobile guys having their carb slides recoated. This builds up the OD of the slide and restores a tight tolerance and returns a steady idle.

Here was my thread on the subject:
http://www.3wheelerworld.com/showthread.php/142062-The-fix-for-the-carb-that-just-won-t-idle?

[webbch]

Didn't realize the starting instructions call for giving it a little throttle while starting. That doesn't seem right to me. I'd think the carb ought to be adjusted properly to NOT need this step.

Wonderboy - that was something I had TOTALLY not considered. Thank you very much for that tip. If my second carb cleaning attempt plus the #38 pilot doesn't achieve the desired results, I will definitely look into the option of having the slide coated. I'll measure the bore and slide diameters while I have it apart though....One could also just order a replacement slide I suppose as well since they're still available for this machine...but I suppose it's the bore that is more likely to have worn (the softer of the 2 materials involved), so coating the slide makes up for a worn bore.

BTW - while the carb dip may affect the bore I suppose, I never soaked the carb slide - I've always just left it on the trike.

[110 atc]

I run a #42 pilot jet in all my 200 Hondas. This will probably make your problem go away. Karl

[bikerboy]

I had this problem on mine, it was bad gas.

[webbch]

Using my telescoping gauges and micrometer, I just measured 0.7880" on the carb bore diameter, and 0.7850" on the slide outside diameter, so I have the same 0.003" variation that Wonderboy had on his slide. I'm going to look into having the slide coated like wonderboy I think.

[wonderboy]

If you can't find any place local by you that can do it for less than $20, let me know. That was the cost by me to have this done. (I can get this to the right guy at the shop here who knows what he is doing).

[webbch]

Thanks. I just contacted the place you linked to in the other thread and am waiting to see if they get back to me.

[shortline10]

Replace the needle and seat and install a stock 200x #40 small jet . If the slide looks worn replace that as well .
Very common problem with these bikes .

[wonderboy]

Omar is the guy you want to talk to.

[webbch]

I'll go ahead and replace the needle, seat and small jet while waiting for the coating place to get back to me. the SLIDE doesn't look worn, but the bore does a little bit (not scratched or anything, just looks like it's been used a bit)...the measurements indicate 0.003" clearance in the bore. I'd expect the bore to wear more than the slide, as the bore is just soft aluminum. Trouble is, I haven't measured a NEW carb to see how much clearance one has when new. I should be able to rectify that issue in a few days, as for $20, I couldn't resist picking up a new Chinese carb just as a backup at least. According to wonderboy, 0.003" clearance can cause idling problems.

[webbch]

I was working on my 185's carb (I think it's a Chinese carb, definitely not OEM) tonight because I'm having the opposite problem with it (idles great, but won't rev). Just for kicks, I measured the bore and slide diameters. The bore measured about 0.0015" out of round , and there was roughly 0.003" clearance between the bore and slide. Not sure how significant that is.

[wonderboy]

Well, given that a properly idling one is at 3 thou, I can't explain my result. Leading up to my installation of the recoated slide, the idle was all over the place. Once I installed the new slide (changed nothing else) my issues all went away. Maybe this is masking some other issue.

I hope it works for you, but I guess as with all advice you get here, your mileage may vary.

[webbch]

I was wondering about that as well. So the slide was truly the ONLY thing you changed? Did you leave the carb body alone (didn't even remove/install or otherwise disassemble and/or adjust) from the time it wouldn't idle properly to the time you sent the slide out and got it back and re-installed? Do you recall if you installed the needle clip in the same position (and same needle) as well? I agree - strange result. I'm no longer convinced that the 0.003" clearance is the smoking gun in my case.

I probably need to try running it again to assess if the idle is too rich or too lean I would think and go from there.

[barnett468]

I recently rebuilt the motor on my 200s (bored cylinder, oversize piston...stock compression ratio, lapped in a new set of valves, etc). It runs great off idle, throttle is very responsive, definitely not lacking in power, but I just can't seem to get a consistent idle. When I set it close to 1400 RPM, it goes between 1000-1600 RPM for awhile and then dies unless I periodically give it some throttle.


The only other pertinent info I can think of.....Hi webbch;


What happens if you set the idle to around 1100?


There are also few questions you haven't answered.


I also just looked at your location. The elevation for benson Az is stated as 3550 to at least 3800. If you are at this elevation, it is possible your bike is actually rich at idle especially if it is stock. As I mentioned previously, the fact it starts easily with half choke suggests to me the pilot jet size is very close if not ideal. Hopefully just 1 jet size one way or another will get it.


Also, I would look at the advance unit to insure it is working freely and does not have a broken spring. A broken advance unit spring can contribute to this type of problem.


Hope you find the problem soon.

[barnett468]

Might just end up being the slide after all.

The bore in the carb for the slide is likely worn more near the bottom then the top. This is caused by the continuous sucking action of the engine on the slide when the slide is in the "venturi". The sucking action causes the slide to drag more on the engine side as it is opened and closed.

If your carb slide bore is .0015" out of round on top might be .003" out of round at the bottom just before it meets the "venturi".

[webbch]

Well, I screwed up when I initially stated I had used the clear plastic tubing the verify the float level. I'd apparently left the fuel turned off during the test. I subsequently repeated the test with the fuel valve on, and the fuel level was a good 1/4" above the bowl. So back to square one, as I can't even START jetting until that's fixed.

I figured, no problem, just need to replace the float needle and/or adjust the float level. Unfortunately, this float doesn't have metal tabs you can just bend. Using my hot air rework station, I heated up the plastic float tab enough to bend it down. When I was started, the float was angled toward the carburetor body a bit. When I was done, it was angled AWAY from the carb body just a tad (I was shooting to get it exactly parallel as a first cut). Anyway, that SHOULD have put extra pressure on the float needle to close it up. I also had a selection of 3 float needles to choose from, and I tried all 3 (the original one, plus 2 additional from 2 different 200s carb rebuild kits I had). None of this had ANY effect on the float level continuing to rise above the float bowl when I did the clear plastic drain tube test. My only conclusion is that the float needle seat is worn out. However, it's not clear to me how to remove it. It's circular in shape with no grab points, and I didn't see how to press it out.

I had ordered a Chinese carb for this model, and given my inability to get the float level sorted out on the stock carb, I decided it was time to try another plan of attack. I opened up the new carb and noticed a #40 slow jet and a #98 main jet. No main jet skirt on this one. The diameter of the airbox side of the intake was identical to stock. The diameter of the port on the engine side was about 1.5mm larger than stock. Also, the slide diameter was slightly larger as well. I transferred my #100 main jet over to it, and decided to leave the #40 slow jet.

I did the float level test with this new carb, and the level was pretty much right AT the float bowl line. Started with the pilot screw 2-1/4 turns out, just like it had came and started it up. After adjusting the pilot screw a little it now idles great, and no longer hangs out at a high RPM. It has a very slight hesitation, so I moved the needle clip down 1 position to the bottom, which improved it, but not 100%. I think I need to go up one size on the main jet still.

It would seem to me that given how much float level has an impact to fuel mixture, that one could almost avoid changing jets entirely, and simply adjust float level instead...other than the fact that it's kind of difficult to adjust the float with a high level of accuracy.

[Iceracer1]

I know your having problems with your 185 as well. Something to consider is that 185's and 200's use the same size carb so maybe you could set this carb up to the 185 to help verify if its a carb problem or an engine problem. Just throwing it out there.

[barnett468]

Well, I screwed up when I initially stated I had used the clear plastic tubing the verify the float level. I'd apparently left the fuel turned off during the test. I subsequently repeated the test with the fuel valve on, and the fuel level was a good 1/4" above the bowl.

I had ordered a Chinese carb for this model,… The diameter of the port on the engine side was about 1.5mm larger than stock. I transferred my #100 main jet over to it, and decided to leave the #40 slow jet. I did the float level test with this new carb, and the level was pretty much right AT the float bowl line. After adjusting the pilot screw a little it now idles great,… It has a very slight hesitation, so I moved the needle clip down 1 position to the bottom, which improved it, but not 100%. I think I need to go up one size on the main jet still.

It would seem to me that given how much float level has an impact to fuel mixture, that one could almost avoid changing jets entirely, and simply adjust float level instead...

AIR BOX - Since your other bike ran much better with the air box lid off, I might do the same mod the lid that I suggested on your other bike and then jet it.

FLOAT LEVEL – Higher is richer, lower is leaner. They are designed to operate within a specific range.

NEEDLE FUNCTION – As was mentioned twice on your other thread, in general, the needle does not affect the main jet. The fact that the hesitation was reduced by raising the needle, suggests to me that you need a smaller needle with the same taper, or a 1 size larger needle jet. This is the brass tube that the needle goes in.


If you want you can do the following, it should get your jetting very close.

RIDING TEST

Do the following on flat to slightly uphill ground.

From a stop in first gear, open the throttle at a slow to moderate speed, 1/3 of the way. If it burbles/sputters before accelerating, it is likely too rich on the needle. If it simply fails to accelerate like it is out of gas or like no throttle was applied before it accelerates, it is likely lean on the needle.

From a stop in first gear, open the throttle quickly 1/3 of the way. If it burbles/sputters before accelerating, it is likely too rich on the needle. If it simply fails to accelerate like it is out of gas or like no throttle was applied before it accelerates, it is likely lean on the needle.

Ride at around 1/2 throttle max [or slightly lower] in second gear then suddenly floor it. If it burbles/sputters before accelerating, it is likely too rich on the main, if it simply fails to accelerate like it is out of gas or no throttle was applied before it accelerates, it is likely lean. If it accelerates smoothly, it is likely very close on the main.


CAMSHAFT – If it has a cam that is much larger than stock you may never completely get rid of hesitation when accelerating from a stop, however it can be reduced by changing your gearing.


PLUG TEST - To further estimate main jet setting, get bike warm then run it wide open in 3rd or 4th gear for around 2 - 3 seconds then turn off kill switch before letting off throttle. Inspect color.

Install a new plug for the plug test, use the recommended heat range. It might take 30 minutes or more to get sufficient color on it to read it properly.


APPROXIMATE PLUG COLOR CHART

WHITE OR LITE GRAY = very lean

VERY LITE TAN = slightly lean

MEDIUM TAN = good

DARK TAN DRY BLACK = very rich

WET GOOEY BLACK = burning oil and possibly rich. Check for ex smoke and smoke color.

[webbch]

OK, so Chinese carb idles great, but hesitates slightly in midrange. Old stock carb was the opposite - wouldn't idle, but rev'd great. Needle/Needle jet controls midrange as barnett468 pointed out. I have the needle as high as it will go, and not quite there yet, but pretty close. I did NOT transfer the needle jet over from the old carb to the new carb, so that would appear to be the path forward on this 200. I'll give that a try and see if it helps.

[barnett468]

Definitely can't hurt to give it a try.

Compare the short part of the needle jet that protrudes into the carb throat. This is called the needle jet choke. The taller it is, the richer it will be, mainly up to around 1/2 throttle.

there are numbers on these as well as on the needles as i mentioned, but again, being chinese who knows what they might mean even if they are numbered.

you can take some number drills [not likely regular ones] and stick them in the needle jet to determine which is bigger. if the old one is smaller it will not help you unless the choke height is higher. confused yet?

if the choke heights are different, it will affect your test.

if they are interchangeable but the old one is not the right size you can buy bigger ones.

how about comparing the spare needle in the carb kit or your old carb as i suggested. a thinner needle is an easy swap.