Clinician
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Post by kancur on Mar 25, 2018 4:15:52 GMT -6
Ok guys, bad news. I sawed the exhaust into two halves, got rid of the catalyst inside. I tested the scooter today with which was basically just a manifold with one half of the muffler - without any air restrictions, basically just a pipe. It didn't work well. It was pretty much the same. Now I'm really confused.
When I disassembled the engine, I noticed a tiny tiny wobble in one of the bearings on the camshaft, so the bearings are definitely not in the best condition, but I don't see that causing that big loss of power.
I'm running out of options. Honestly, I can't imagine what can be the cause. Can it be something electrical like CDI? Or is it running bad just because it had no backpressure?
So to sum it up:
The engine runs smoothly and nicely but has no power. It's bad with and without the muffler. Valves are good. Valve gaps are good. The timing chain is correctly set. The engine has new oil. Runs bad with and without the air filter. Runs bad whether the needle in the carb is in the lowest or highest position. I checked valve springs and they are not broken. But I can't say for sure for the inner one, I couldn't visually check that one. I can imagine how this could become a sudden problem with results similar to mine. But pushing them with my fingers is very difficult so I don't know....
One of the main important things to note is the way the problem developed.
I was running WOT on the city highway when it SUDDENLY started losing power and lost most of the power in a few seconds. I was happy that there was an offramp in 2 minutes.Since then it basically has no power. It's sluggish and slow. But engine runs nicely, no bogging or anything. But during my first ride after the problem developed, it was actually firing into the exhaust sometimes and losing power completely. Now it works fine, but has no power.
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Post by cyborg on Mar 25, 2018 7:51:15 GMT -6
Check the cam timing,,,chain may have jumped a tooth or two
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Clinician
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Post by kancur on Mar 25, 2018 12:21:27 GMT -6
I've checked it. I've had the whole engine disassembled. But will recheck probably soon. Cannot this be caused by some electrical problem like spark firing a little too late? Something wrong with CDI?
Edit: Thinking about it. I really need to check my timing chain again.
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Clinician
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Post by kancur on Apr 5, 2018 7:47:59 GMT -6
Ok, I checked the cam timing. Not just against the mark on the flywheel but also checked the real position of the piston. It's not a timing issue. I'm really really running out of options!
Can a CDI be faulty in such way that it would cause these symptoms? I'm really lost.
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Clinician
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Post by kancur on Apr 9, 2018 9:55:06 GMT -6
Ok, tested a new CDI. Still the same. I tried a lot of stuff today.
If the engine is OK, electricity and ignition is OK, Fuel delivery is OK, Exhaust is OK,
then the problem should be in the carburetor.
I tried various needle level settings for richer and leaner mixture, anyway unplugging the air filter helped a lot - I therefore believe it runs rich. But why? I set the needle to the lowest position so the mix is as lean as possible without changing the jet (I don't have any other than original one). It's still not working very well. I'm pretty tired of following plenty of dead ends already. I don't have much ideas.
Another interesting note:
Unplugging that strange emission hose that goes from the head to just before the carburetor helped very much. I think it's for recirculating the blow-by air or something.
Thank you guys
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Post by cyborg on Apr 10, 2018 8:09:14 GMT -6
Check the carb diaphragm,,,it may have developed a tear,,,pull the top of the carb you'll see any problem right away when you take out the slide
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Clinician
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Post by kancur on Apr 11, 2018 5:36:42 GMT -6
Yeah, I tried different diaphragms and noticed that one of them is not rising. Unfortunately I now don't remember which one was originally there few weeks ago when the problem happened, but definitely could be the cause!
The scooter now drives much better.. can even get to 70 kph (43mph) But still lacks power - I'm pretty sure it's running rich. I read somewhere than now more free-flowing exhaust could cause rich condition. So I ordered smaller jets and will test it. Will report here, but will take a few weeks till they come from china.
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Post by czmdiver on Apr 11, 2018 8:08:05 GMT -6
Oposite on the Jetting, Have to fatten up the jetting for a hot rod exhaust..
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Senior Clinician
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Post by solymar on Apr 11, 2018 15:41:06 GMT -6
I agree with czmdiver, a free flow exhaust will cause a lean condition, you’ll need to use a bigger jet to correct it.
Solymar
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Clinician
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Post by kancur on Apr 11, 2018 16:27:41 GMT -6
Now I'm even more confused. The back of the exhaust is black and sooty, if I hold a handkerchief for 10 seconds there, I see black residue on it.
So maybe, it's rich on idle, but lean on WOT.
Anyway, I ordered smaller jets and bigger too so I will test that too.
But why does it run better without an air filter, and without that gas recirculation hose that goes from the rocker arm cover (those blow-by gasses or what is it)?
Thank you guys for your ongoing support! :-)
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Clinician
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Post by kancur on Apr 30, 2018 7:25:37 GMT -6
It seems like you are right about it not being rich. I tried smaller jet. It run terrible on WOT. Tried bigger than original jet, it runs probably better. But still nowhere near good as before. Tried different sizes but still don't know. It seems to me that it runs better without air filter on, so will buy a cheap open one. But I still don't understand why it's not working as before. So confusing. ![???](//storage.proboards.com/3059616/images/uQfospbezE7IcMUG1AtY.gif)
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Post by bengr8 on Jul 4, 2018 12:20:05 GMT -6
This post is kind of old but did you check the plug wire? It has a coil on the end that could be bad. Mine was bad and the plug still sparked and was hard to start and underpowered until i changed it.
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Post by kancur on Jul 11, 2018 11:07:38 GMT -6
Well, I already changed coil in the past. Can try it. The state right now is like this: Don't forget I sawed of the catalyst- it did not help at all ![:D](//storage.proboards.com/3059616/images/j7oliHrgM6d9allIZs7k.gif) (I though it must be plugged or something). Scooter runs OK, I use it daily, but lacks power It' difficult to get to 60 km/h - while it was easily doing 90 km/h before. The acceleration is sluggish. Occasionally it backfires on deceleration (or how it's called). The missing power is very noticeable when going uphill. Basically it rides like a 50ccm 4 stroke scooter. I will have to investigate some more to find the cause probably. :/
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Post by gigster2000 on Jul 31, 2018 3:25:00 GMT -6
As far as the exaust goes youmay have lot a lot of back flow wich will also result in power loss at high rpms so ive been told.
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Post by gigster2000 on Jul 31, 2018 3:30:07 GMT -6
Have you considered rear end oil variator/roller weights and a new belt Also check tire pressure
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