1987 NQ50 Running Issues

[Nate4s]

Is your fuel petcock functioning properly? My elite had all kinds of wierd tuning issues when it wasn't? Are you sure it's running lean on the low end? And it sounds like the carb is clean I'd look at the air filter make sure all is well there. Have you burned out the exhaust pipe to make sure it's not clogged?

The petcock is functioning normally, as far as I can tell. If I manually suck on the vacuum line, fuel flows out easily and stops flowing after I sucking on the vacuum line.

I'm not positive it's running on the lean end - in the past, whenever I've pulled the plug, it's always oily or has carbon build up on it. I would have assumed that's indicative of it being too rich. However, it runs perfectly when it first starts up and starts running poorly once it's warmed - making me think once that bystarter extends and cuts off the extra fuel, it's too lean. I've burned the exhaust and treated it chemically (drain cleaner).

I am almost positive now that this is an air-intake/air-box issue. It has the screw, the lid, the gasket, the elbow, the stock air filter (oiled to spec) - so I don't know where to look for the leak/issue. The person who owned it before me had modified the stock airbox, but I just patched up the hole they drilled with epoxy. I'm not sure if they modified it in any other way or cut any parts out. Any thoughts on what to look more closely for?

[vintagegarage]

"It starts and runs great (good acceleration, good idle) for a minute, but after riding it for a bit (it runs great at top speed), it has terrible acceleration - and I mean TERRIBLE. I'm barely able to keep it balanced for the 20 seconds or so it takes it to get to 15 mph, after which, it takes off quickly. My '86 spree accelerates like that all the time. Any other thoughts of what this could be?"

My Spree did the same thing and it was just the clutch slipping when it got hot. I swapped my clutch for a spare used one and now it takes off like a jackrabbit. The odd thing was that the shoe thickness was about the same on both of my two clutches (original and used spare). After I got my good Spree running right, I used sandpaper to rough up the original clutch pads that had been in it, which were pretty much glazed, and put that clutch in my parts Spree, and the parts Spree now has good takeoff speed as well. I am not sure if sanding the pads is a good fix to a bad clutch, or if I just got lucky.. maybe others will comment to let us know. In any event, I don't believe the clutch pads are still available new from Honda, at least, I couldn't find a new set.

Also, be very sure that you have the idle speed set slow enough so the clutch is fully disengaged at idle. Also be sure that your rear brake is not set so tight that it drags at all, or it will drag more when it gets hot. With the Spree idling, it should definitely roll backwards down even the slightest incline. If it doesn't, your clutch may be dragging and that will get it hot in a hurry.

[Nate4s]

"It starts and runs great (good acceleration, good idle) for a minute, but after riding it for a bit (it runs great at top speed), it has terrible acceleration - and I mean TERRIBLE. I'm barely able to keep it balanced for the 20 seconds or so it takes it to get to 15 mph, after which, it takes off quickly. My '86 spree accelerates like that all the time. Any other thoughts of what this could be?"

My Spree did the same thing and it was just the clutch slipping when it got hot. I swapped my clutch for a spare used one and now it takes off like a jackrabbit. The odd thing was that the shoe thickness was about the same on both of my two clutches (original and used spare). After I got my good Spree running right, I used sandpaper to rough up the original clutch pads that had been in it, which were pretty much glazed, and put that clutch in my parts Spree, and the parts Spree now has good takeoff speed as well. I am not sure if sanding the pads is a good fix to a bad clutch, or if I just got lucky.. maybe others will comment to let us know. In any event, I don't believe the clutch pads are still available new from Honda, at least, I couldn't find a new set.

Also, be very sure that you have the idle speed set slow enough so the clutch is fully disengaged at idle. Also be sure that your rear brake is not set so tight that it drags at all, or it will drag more when it gets hot. With the Spree idling, it should definitely roll backwards down even the slightest incline. If it doesn't, your clutch may be dragging and that will get it hot in a hurry.

Good to know - thanks! I've been leery of my clutch since day one, but you're right, they no longer sell new clutch pads. I bought some new clutch springs, but haven't had a chance to test those.

So, new information to add to the list of "things" to help narrow down the issue. I started it up and let it idle for about 15 minutes. Turned it off, and then couldn't start it again unless I used WOT during the starting process. I put in a new plug (my old one was black and sooty...which would suggest to me that it's too rich, which makes NO sense to me) and no change. I don't get it. The starting process seems too lean, but the plug seems like it's rich. Thoughts?

[vintagegarage]

My experience is pretty limited, but it tells me that if you need WOT to start it, then your idle mixture, i.e. air bleed screw is not set properly. While the engine is fully warm and idling, and you screw the bleed screw in a half turn from where it is now and then out a full turn, there should be a very noticible change in idle speed. if there is no change in the idle speed, then your air bleed circuit may be plugged up. When everything is right, and the engine is warm, starting should be instaneous, with your hand completely off the throttle, and you shouldn't need to touch the thottle until you are ready to drive off.

[Nate4s]

My experience is pretty limited, but it tells me that if you need WOT to start it, then your idle mixture, i.e. air bleed screw is not set properly. While the engine is fully warm and idling, and you screw the bleed screw in a half turn from where it is now and then out a full turn, there should be a very noticeable change in idle speed. if there is no change in the idle speed, then your air bleed circuit may be plugged up. When everything is right, and the engine is warm, starting should be instantaneous, with your hand completely off the throttle, and you shouldn't need to touch the throttle until you are ready to drive off.

There is very little difference in the idle mixture screw being between 1.5 turns out an 3.0 turns out on idle speed. Any less than 1.5 turns out and it starts to bog - but, even screwed all the way, in it doesn't actually kill the scooter.

[vintagegarage]

something is wrong there. It should die when the air bleed screw is turned all the way in, or out 3 turns or more, unless you have your idle speed screw turned too far in. It should be easy to find the best setting for the air bleed screw, as idle speed will decrease if you go 1/8 of a turn in either direction of perfection. Start with your air bleed screw out 1.5 turns, get the bike running by using WOT as needed, then let it idle and then back out the idle speed screw until the motor almost dies. Then turn the air bleed screw in and out 1/4 turn and let us know what you find.

[Nate4s]

something is wrong there. It should die when the air bleed screw is turned all the way in, or out 3 turns or more, unless you have your idle speed screw turned too far in. It should be easy to find the best setting for the air bleed screw, as idle speed will decrease if you go 1/8 of a turn in either direction of perfection. Start with your air bleed screw out 1.5 turns, get the bike running by using WOT as needed, then let it idle and then back out the idle speed screw until the motor almost dies. Then turn the air bleed screw in and out 1/4 turn and let us know what you find.

Yeah - I'm not fond of the way it's running and the non-characteristic way the carb is operating. The problem with it is that once it's warmed up and I need to use WOT to start it, the idle speed is terribly low already (just barely enough to keep it running).

EDIT: Just tested the bike. Since I bought it from the previous owner, it's having the same issue: the idle speed, even when it's seated all the way in, doesn't allow the bike to idle higher than 1,500 rpm (not tested, estimated based on my other motorcycles). For about the last 3 turns inward (until seated), it has no effect on the idle speed of the scooter.

[vintagegarage]

I think if your idle circuit is blocked, you can make the engine idle by screwing in the idle speed screw far enough to lift the carb slide high enough so that the engine idles (pretty roughly) on the main jet instead of the idle circuit... not sure about that though. With the engine turned off, and everything cold, unscrew the air bleed screw all the way out, and then insert the end of a air blow gun into the air bleed screw hole with a moderately tight fit. Wrap the end of the air blow gun with masking tape if you need to get a tight fit, but be careful not to damage the air bleed screw threads. Hit the trigger on the blow gun and gasoline should fly out from all parts of the carb. If it doesn't, something is blocked in your idle circuit, or the fuel bowl is empty.

[Nate4s]

I think if your idle circuit is blocked, you can make the engine idle by screwing in the idle speed screw far enough to lift the carb slide high enough so that the engine idles (pretty roughly) on the main jet instead of the idle circuit... not sure about that though. With the engine turned off, and everything cold, unscrew the air bleed screw all the way out, and then insert the end of a air blow gun into the air bleed screw hole with a moderately tight fit. Wrap the end of the air blow gun with masking tape if you need to get a tight fit, but be careful not to damage the air bleed screw threads. Hit the trigger on the blow gun and gasoline should fly out from all parts of the carb. If it doesn't, something is blocked in your idle circuit, or the fuel bowl is empty.

Unfortunately, I don't have access to an air compressor. Also, I have a spree that runs great, and swapping the carb from that scooter to the '87 that's not running well has literally no effect. What else, besides the carb, would be preventing adjusting my idle screw from having little to no effect? Any chance it's the CDI or other electric component? It just really seems like a fuel issue, but all of those systems have been investigated...

[vintagegarage]

Swapping carbs with no change is pretty convincing evidence that the problem is not in the carb idle circuit so forget my suggestion about it.. the CDI box is easy to switch between your two Sprees as well.. a bad CDI seems unlikely, but they are so easy to change, you should do that.

Also do a compression check and compare the two Sprees.. compare them with both closed and WO throttle.

When you swapped carbs, did you do the extra work to swap the carb valve (slide) and needle as well, or did you just save time and test both carbs by using the slide and needle from the one that won't idle right?

Somewhat more work, but swap the entire airbox, filter, and elbow between the two Sprees.