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Post by bjg on Nov 13, 2012 7:58:53 GMT -5
I had a thread going on this a while ago but I can't seem to find it now. Anyway, here is what is going on.
My scooter is extremely hard starting. Once started it runs great. It idles at about 1700 rpm warm and holds that just fine. Top end is good and I have smooth acceleration throughout. My battery is strong at over 13vdc and it holds that even during starting. My starter cranks without issue. I had a bad enricher (it was cracked and wouldn't extend/retract properly when hot/cold) and i replaced it but symptoms did not improve. I also replaced my spark plug as the old one was a little carbon fouled but that didn't seem to help either.
I know that I am not supposed to crack the throttle when starting but it seems to make it start easier, especially if I have been cranking for a bit and then crack the throttle while trying to start it. I'm guessing that my air/fuel ratio is bad but I'm not sure what to do next.
I've been looking at the carb for an air/fuel mix screw and I think I found it (on the engine side on the bottom of the carb) but it is plugged. Before I go removing the carb to get the plug out, is there anything else I should check? I'm thinking my jets are ok because it idles and runs fine. I'm new at this but I think if I can get the air/fuel mix right my scooter will start properly. Any help here would be appreciated.
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Post by ootscoot on Nov 13, 2012 9:41:38 GMT -5
could also need a valve adjustment
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Post by bjg on Nov 13, 2012 10:18:06 GMT -5
I can definately check the valves but could a valve problem cause it to start hard and run great when started? Again, I'm new at this but I would think I'd have other issues if it were the valves. I'm not doubting you. I'm just trying to become more self sufficient with diagnosing my scooter engine so any insight into these things is helpful.
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Post by jlee on Nov 13, 2012 12:03:02 GMT -5
If the valve lash is too tight, the valves won't fully seat and you'll lose some compression, making it hard to start. The engine may run ok, but it will run even better once the valves open and close properly (plus it will start easier).
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Post by richardthescooter1 on Nov 13, 2012 15:28:19 GMT -5
here is the carb on a mc-54-250b if thats yours? Attachments:
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Post by skuttadawg on Nov 13, 2012 15:33:04 GMT -5
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Post by richardthescooter1 on Nov 13, 2012 15:46:49 GMT -5
Big, I'd check the intake manifolds and clamps and vacuum line, any leaks you will be too lean and that willcause hard starting also. When replacing spark plug, did you look to make sure spark plug cap was on tight and the wire inside is making good contact with spark plug?
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Post by bjg on Nov 14, 2012 7:02:44 GMT -5
jlee - thanks for the explanation. I had thought since it runs good once it starts I was ok but I suppose ther could be a valve problem. It isn't hard to check it anyway.
richardthescooter1 - The pic above is my carb and you confirmed the location of what I thought was the air/fuel mix screw. I've replaced all the vacuum lines and put new clamps on and I've checked everything is tight. The spark plug cap clicks into place and it feels seated firmly.
skuttadawg - thanks for the link. I had downloaded that a while ago but I've never been sure exactly how much of it applies to my 250cc. I know the wiring is different. I did look through the TS section on hard starting and I've done everything except a compression test. I don't have the tester (yet). I was thinking that my compression should be ok since it runs good once it starts but maybe I need to rethink that.
I was thinking that I'm running rich because my plug had some carbon fouling and because it seems to start easier when I crack the throttle. If I read it right, that bypasses the enricher and dumps air in so the air/fuel ratio changes towards lean.
I'm think I'm going to pull the plug on the air/fuel mix screw, check the valve gaps, and maybe pick up a compression tester. I suspect the guy that had this scoot before me ran into these problems which is why I got a sweet deal on the scooter. It was starting and running ok then but it was a lot warmer out. Ah well, I'll get it eventually. Thanks everyone for the help.
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Post by richardthescooter1 on Nov 14, 2012 10:01:38 GMT -5
Big, Talking about that enricher, make sure its seated also, if not air could make it lean and the results would be hard starting too. Two day ago I had problem with mine not starting and cranking it to the point of a dead battery (Yup, intake look tight, but was loose, tighten it up and it fired right up, I'll post a picture of what else it could, it happened to, I fix it temporary, but need to buy a intake manifold.
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Post by richardthescooter1 on Nov 14, 2012 10:03:31 GMT -5
This happened to me, cut in intake, clamps were tight, no start until I fix this problem. Attachments:
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Post by bjg on Nov 14, 2012 10:24:20 GMT -5
Nice....right under the clamp so you couldn't see it until the clamp was off. Ok, I'll check for that too. Thanks!
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Post by rerun2 on Nov 14, 2012 23:50:59 GMT -5
An easy way to check for vacuum leaks is to get the engine running and spray starting fluid around the potential leak areas. You will get a definite engine surge if you have a leak, so make certain you do this while on the center stand and NOT the kick stand.
Valves are all ways a good think to at least check. If the prior owner was having these starting issues that could very well be the source as a lot of folks will not think of that.
One thing to keep in mind, every bike is different to some degree, if yours needs a little throttle when it is cool out to get cranked, it is not a big deal at all, it could be just the cure. Burning out your starter and draining your battery is certainly more of a concern in my thinking! All batteries have a limit to the discharge/recharges they are capable of, even more so if it an original low quality Chinese one!
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