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Post by scooteraddict on May 19, 2012 18:45:40 GMT -6
I have a MC54-250B and something doesn't seem right. Now, just so that you guys and gals go off on a tangent about the Carb or fuel issue, I have confirmed that I'm running just to the rich side by a wide band o2 sensor.
Now what I need your opinion about is that I can't seem to get by 250 past 6k rpms. Do you think that this might be due to to a rev limiter? Has anyone else experienced this as well?
I was thinking to upgrade to a performance coil and or CDI. Has anyone done such an act? If so, with what brand and what results?
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Post by scooteraddict on May 11, 2012 15:38:07 GMT -6
[/quote]Do your rear shocks have adjustable preload settings? They may be cranked up too high. My scoot (YY250T 244cc Honda clone) has adjustable rear shocks. I am running 26 pounds of air in the front and 32 in the rear with the original tires. The rear shocks are set to the softest setting. I have no complaints with the ride quality. The rear gives me a very comfortable ride while I get a little road feedback from the front. Check your tire pressure and shock settings (if any) - it can make a big difference.[/quote]
Unfortunately my shocks have only a spring with a fixed plate. I've been looking around but some of the shocks that I've seen are more expensive then car shocks. Go figure.
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Post by scooteraddict on May 8, 2012 17:03:37 GMT -6
Even with the Avon (soft) tires, my shocks are so stiff, I still got a bumpy ride. I don't thing that it will make a difference.
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Post by scooteraddict on May 7, 2012 11:09:41 GMT -6
I ran with the Avon Viper 130/60/13 and the tire didn't last. As I went to deflate it the tire folded in half. Didn't get nearly 3k out of them. I'm looking for longevity and I'm hoping that the tire that I have now will work. These are recommend for the larger 400 and 650 Scoots.
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Post by scooteraddict on May 6, 2012 17:54:27 GMT -6
This I know. I'm hoping that the tire doesn't grow that much. I can tell you the the Dunlop tire that I used is that it's a very stiff tire. I'll see very soon due to the fact that I need to replace the swing arm.
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Post by scooteraddict on May 6, 2012 16:00:14 GMT -6
As the title states, I have a few things to pass on to those who own a MC-250B scoot. These things are answers to the reoccurring questions that I see all the time this forum. For the first question, does a larger tire fit onto a 250B scoot. The answer is yes but it’s very tight. I recently had a 130/60-13 tire that only lasted about 3000 miles. This was a Avon viper striker tire which didn’t last nearly 1 ½ seasons, so I decided to get another one. After looking for a few weeks, I decided on a really nice Dunlop tire. The only problem was that the size was a 130/70-13. Taken a chance, I purchased it and place it on the rim. When I went to install it, I found out that it wouldn’t fit on without some disassembly of the bike. What I mean by this that the seat bucket and right shock had to be removed. Once this was done, the tire had to be void of air as well. After fitting it on, I filled up the tire with air and turned the wheel. Well when the wheel turned, I was hearing a rubbing noise however this was due to the extra rubber from molding the tire. Unfortunately I haven’t had a chance to ride it to see if it really interferes with rubbing against the engine with pressure against the tire. The next thing is for those who are looking for 250B parts especially rear rims, they have them and they do fit. I place an order for one since day one the original rim had a slight bob to it. After checking the VIN and found that it started with 5RY and used the scooter with the designation of being a 5RY on the web site, I decided to give it a try. Yep, it was the right rim. Ship to me within a week since I live is NY and it was coming from CA. For all those who have complained about rear end wobble, there are several things to look at. The first is to look at the nut on the axle. This tends to loosen up and allow the rim to become loose and move on the spined shaft. Replace the nut. Better yet get another nut and use a jam nut to lock it in place. If the shaft nut is tight, the next thing is to look at the engine swing bracket bolt. This nut and bolt that is in the lower section of the bracket that attaches to the engine has a tendency to loosen up as well. I’ve had this issue for some time and with the seat bucket out I had a better chance to see it wobble clearly. I broke out the wrenches and tighten it up and the wobble was no more. This is another area where you would want to place a second (jam) nut against the original one. This will lock it into place and prevent it from loosening. I hope that this has help some of you that has asked these questions and what to do.
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Post by scooteraddict on Feb 18, 2012 19:43:26 GMT -6
From what the diagram shows is that there should capacitor a cross the red and yellow wires. One side of the power would go to the blue and the other to the black or white. Don't try it without the capacitor or it won't work.
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Post by scooteraddict on Sept 8, 2011 5:40:20 GMT -6
I came across an article that I found interesting. .innovatemotorsports.com/resources/rich.php" rel="nofollow" target="_blank">.innovatemotorsports.com/resources/rich.php Although it talks about turbocharging, it explains the principle of running too rich can have an effect of a poor running engine. In the short, this quote explains it all. "Therefore a richer mixture releases less energy, lowering peak pressures and temperatures, and produces less power." Recently I have experienced this effect due to a bad enrichener which was making my bike run very rich. The end effect is that when the bike required high torque under load (mainly going up hills), I would loose power and it would seem like it was bogging down. Once I replace the enrichener, and tuned the bike with a new jet, it is running like a champ. I was able to achieve more power for hill climbing and higher speed on the flats. For those who post that they can't get power for hill climbing, please take note that this might be a cause for your problem.
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Post by scooteraddict on Sept 6, 2011 18:20:10 GMT -6
Well it turned it that it was too rich to the point that it was quenching the spark. With trying to run under full torque the cylinder might have been so wet that it couldn't burn correctly.
What I found what the problem was, the auto choke wires broke at a heat crimp for the plastic tubing that encompassed them.
I wrote another thread that explained all the issues that I encountered this year due to this issue. Long story short, after putting a new choke in, it make a big difference with the need to and including upping the main jet by one.
The thread, if you want to read it is under the title "A problem and the fix with a 250B" under the 250cc section.
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Post by scooteraddict on Aug 27, 2011 20:18:35 GMT -6
At WOT, the butterfly valve open full, the vacuum slide will stick. The round slide with diaphragm on top. The throttle will return to normal but the slide will stay elevated. I would have to take the top cap off and reset or unstick the slide as to the proper position.
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Post by scooteraddict on Aug 27, 2011 13:30:57 GMT -6
Now that I have my bike (a MC 250B) running like a top, I have a small problem with the Carb. It seem that after starting the bike cold and taking it for a ride at high speed, WOT, the Carb like sticks. Can't tell if the needle is coming out of the seat or the slide just gets hung up. Since I had just recently tuned the Carb which I can achieve speeds of 80mph (chinometer reading). What I,m thinking is that the vacuum at that speed is so great that its raising the slide too high.
Any ideas to combat this problem?
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Post by scooteraddict on Aug 21, 2011 19:14:59 GMT -6
What size main jet are you running? Also, have you checked your float? Does it seem like its bogging, if so you might be too rich?
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Post by scooteraddict on Aug 20, 2011 19:50:38 GMT -6
I just did a post called "A problem and the fix with a 250B". You should read it.
In the end, basically i stated that my problem, almost same as yours, I was flooding the engine. You might be running too rich as well.
Have you messed with your jets at all. you might have to drop a size or look at your choke.
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Post by scooteraddict on Aug 20, 2011 11:58:32 GMT -6
Thanks. I was hoping that it would convey a message and not be some long drawn out story.
What I also failed to mentioned in the story is how the the exhaust sound had changed to a deep throaty sound. This would have been an indicator to being with. Now by trade, I work as a machine mechanic and I have trained myself to diagnose through sight, sound and feel. I guess that after a winters nap, I lost what the bike should be like. Every day, I learn some thing new.
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Post by scooteraddict on Aug 20, 2011 8:57:49 GMT -6
Now I know that this forum is a place that we riders can ask for help and talk about anything including off the subject topics. Well this thread is not about asking for help or bitching about how my ride is a POS but a tale on my troubles and woe’s for this riding season and what I discovered to get my ride running again.
To give you some information about my ride, it is to be considered a MC250B with the Linhia engine running with an 856-23-30 belt, 12 gram sliders and a K&N air filter with a pre-charge filter (mesh net for fine dust). At the time, about 6800 miles getting in the hi 60’s to low 70’s Mpg and topping out at 73Mph’s (Chinometer) or true 68Mph’s. I have toyed with the carburetor in getting the bike to run optimum using a temporary O2 sensor rig. With this rig, it allowed me to dial in the pilot and main jets so that I can get the most out of my air/fuel mixture without being too lean or too rich. I wound up using a slightly opened up 115 main jet but not as big as a 118. I was able to turn a maximum of 6k Rpm’s, on a REALLY good day (not often), 6.2k Rpm’s. As of last year the bike was running great as far as my opinion except for when it would warm up. What would happen is that when the bike was still cool and choke would start to close (about after one minute), the would stall.
This tale starts right from when I take my ride out of its winter nap. The beginning of the riding season is lower NY was not so good and I wasn’t getting much a chance to ride as often as I wanted to. I did notice that something was funny with the bike and that the idle was erratic. It would start up and speed up as per the choke and then slowly settle down into its preset idle. But what would happen is that there would be times that after the bike was warm, the idle would be too high, about 3 to 4 hundred Rpm’s higher and time it would be normal. After adjusting the idle screw several times over the course of early riding season, about 5 or 6 times, the bike would not do this anymore. I just contributed this to the cooler weather that we have been having.
It came to about mid July that I took the bike out for a ride to drop something off for my daughter, which the road I was traveling on was hilly and curvy. As I was riding I noticed that the back end would be sloppy and thought that I was getting a flat however the tire was fine. What it turned out to be was that the swing bar that mounts the engine to the frame was sloppy and had too much play in it which allowed for a good amount of back and forth movement of the engine to travel. As I proceeded to repair this problem, I discovered that the inner metal tube within the bushings were wearing out and causing slop which allowed the side to side movement. Since I was having trouble trying to find the bushing required for this fix, I became innovative and rigged something else up which created a stiffer pivot point. And it worked great.
Now this is not were the tail ends, in fact I still had problems. While I had the bike dismantled and covers off, I decided to readjust the valves because of convince. Set the valves at 0.004” for the intake, 0.006” for the exhaust. (I followed the Yamaha manual for these numbers) and took off the pre-charge filter. I even toyed again with the main jet, opening it up just a little further but still not yet a 118.
Now that the bike was back together, time for a test ride. My first true test ride, you know, ball to the wall, full out WOT hill climbing test to put it through its paces. Well I can tell you the steadiness feel of the newly reinvented bushing were great but what I discovered was that I was having a fuel issue now. What went through my mind was, “why did I mess with everything else when the bike was working so great”. You know, if it an’t broke, don’t fix it. Now, I was pissed. What I was experiencing was, at WOT on hills, I would start to bog down a little and loose Rpm’s dropping to 5.8k or even 5.5k Rpm’s. Mind you, I would still achieve top speed on flats with no problem but it was the hills that bothered me since where I live, we have quite a few.
After posting and looking for questions, someone mentioned that the exhaust should be 0.005”. And the plastics came off again and the exhaust was readjusted but I was still having the same problem. Someone even suggested that the bike was starving.
Next I replace the pre-charge filter, thinking that I was getting too much air but no change.
One last thing I did was to reinstall my O2 rig and see what was happening at WOT on hills. To my surprise, I was running rich, more like too rich. After thinking, maybe I opened the main jet too much. Now really angry, my next thought was to start back at a fresh 115 main jet but I had to let it go for now because all this work was for getting my ride ready for Myrtle Beach, SC and no way to get the jet in time. Since it was mostly all flat, I felt that this would have to do. (I had a good time there by the way.)
Well, I’m back home now and figured I should get to the bike shop and pick up a new 115 main jet which I did. Opened the seat and pulled the access hatch and pulled the carburetor out. Opened the fuel bowl, replaced the Jet, took out the diaphragm (which holds the needle jet) and gave the carburetor a good shot of carburetor cleaner. I then reassembled the carburetor and inspected it before I replace it. Low and behold, guess what I found? You’ll never guess, go ahead and try. Give up? Well the wires to the auto choke were broken. Right were the tubing was heat crimped before the wires entered the choke. Both wires separated but never pulled a part due to the tube melted to the wire sheathing and holding them in place but with enough space to not allow them to touch. This all makes sense to me now. Remember that I told you that the idle would vary 4 to 5 hundred Rpm’, also that the engine was running too rich. The varying Rpm’s would account to the wire making and braking causing the choke to work then not and the engine running too rich when the wires finally separated all together. As far as the problem with for WOT on hills, I can only think that too much gas was quenching the spark and not getting correct burn when the bike required full torque needed of hills.
So I replace the choke with a spare one that I had which concerned me because the new of the replacement was out further than the original one. My thinking was the now the choke would close off faster and not give me enough gas when cold. To my surprise, the choke worked better then the first one which wouldn’t allow it to stall. Now came the test ride and found that with the new main jet, I was running lean. I had discovered this by feel due to when on the hill at WOT and I backed off, I can feel a slight surge meaning that the carburetor slide would close and burn the extra residual gas left inside the intake. So one more time the carburetor came out and this time I went with a 118 main jet, not the original one I had been working on. Then I took it out for a quick test ride but couldn’t really get any results due to rain slicked wet roads.
The real test ride came this morning when I took the ride to work. A 25 mile or so test ride with both hills and flats. Once again, I shook my head in disbelief. It was running much better than ever. On the hills, she reacted as last year, the engine maintaining 6k Rpm’s with a little lost in Mph but on the flats, instead of topping out at about 73 chinaometer Mph’s, it was topping out at around 80 Mph with a top Rpm of 6.3k right in the maximum torque band. The only thing that happened once I got to work, I had a problem and that was, at low speed, I would give it throttle and the bike wanted to die. If I let off of the gas it would stay running. What this problem was is that the needle jet came up to high out of its home and jammed the slide in the full open position.
Now I know that this is a long winded tale but I was hoping to give some insight as to what happed, the effect it had and the results of the correction. For those who really read between the lines and have experience problems that I have mentioned, I hope this helps in solving your problems as well. One being too little or too much gas can cause problems. Unless you dial in you jets correctly, you can experience problems.
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