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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.

No. That seems normal however I recently drained some of my system and then refilled it up again. This time around I made sure that I completely got all the air out. Now the gauge will be about the 1/3 mark and the fan turns on then the temperature rises above the 1/2 mark at which point the fan turns off. Go figure.

Try roketa.com/product/product_support.jsp?cateID=2610&sonCateID=0&proID=27312

No problem with the butterfly or cable. IT IS the slide.

When I experience the symtom after slowing down and giving it gas from a closed throttle, I experience a slight lag, then it picks up.

When I notice this I pull over and remove the Carb top to the diaphragm and it is stuck up in an up position. A slight touch will knock it down again.

As far as the main jet (a 118) being to big, the next lower one would cause the bike to run lean.

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.

First I would like to say that I love these forums. Great information and all.

Now. I'm in a bind and need expert help.

Well after riding one day on a wavy road one day, I noticed that the rear end was wobbly. I pulled over thinking that my tire was going flat but it was fine. After further investigation, i found that the bushings on the lower haft of the swing arm were worn.

Now I have been searching for a while and can't find the bushings that I need.

What I need is a bushing that is 25mm OD x 10mm ID x 30mm w however the exact center is actual 72mm long.

I'm at a lost and really would like to get the bike up and running again before I go on vacation in two weeks.

Anyone might know where to purchase one?