Jumping logs is a technique issue rather than a power issue. I suggest you ride some Trials events and work on learning good technique.
Handguards are invaluable if you need to plow through brush.
motovita- I try to stay on the trails pretty much, so not a lot of brush busting on my rides, and the full wrap around brushbusters seem like overkill - more weight and expense. Unfortunately in my area there are very few trials events within driving range. I can't find a seat option (Trials type seat pan and cushion that is designed for trials for this bike. ) Also my suspension system is pretty stiff for clearing logs- seems like it's bottoming too easy without moving much and the rear shocks are also not moving much- makes for a fairly rough ride. - can't find any help for either one of these problems!
Feetup fun- That's good to know information! I was all ready to remove that band and give it a whirl, but sounds like it's not that good of an idea after all. You probably saved me a lot of heartache! But question- I had been running a 12-53 and first gear speed is "too low" to be of much use for trail riding- it takes valuable time to shift thru first, second and you are not moving fast enough to give the wheels any "gyro effect" so there is not much stability until you are moving at about a fast walk at least. So first gear is almost useless. So I put on a 13 tooth front sprocket and that is more "user friendly" my shifting is a bit less often and I'm not needing to change gears as much while reaching a stable speed. Seems like about 10- 15mph is a good starting point. My new boots are stiff enough that you need a definite effort to shift, and that gets old pretty fast on the trail. I'm almost 72 now and that has a lot to do with all this, but do you think a 14-53 is better all around or a 13-53 for single track? Some of the trails here are rocky and fairly steep. I also am looking into Boyesen reeds or anything else that would help me jump a log When- not IF that becomes necessary. What is your opinion on Barkbusters and what tools you carry if you are 20 miles from the truck?
Here are a few observations I have made with my 12-53 ratio riding on the TY 250 A-
#1 the "Granny low" first gear is a mixed blessing for trail riding- Can't say I don't use it at all, as I do get into tight "dead stop" situations where the front wheel is against a rock and there is no way to get a run at the obstacle and use momentum. However, it's a pain to have to shift twice or three times to get moving again and really enjoy the riding. I'm not sure why, but standing on the pegs and tying to shift is not my favorite thing to do. There is always that jerking and trying to balance while absorbing the speed changes and rocky terrain that makes balancing such a tricky manouver.
I probably made this a little harder myself with my "oversize" foot pegs. They are about 5" wide and 3.5" front to back. Your foot cannot really rock on the left side because the pegs are so big. - back to the drawing board on that one- I have some "drop mount" plates that came with the bike, but they put your feet so far back that you have to stretch and bend forwards while standing to reach the handl bars- even with the 2" risers I have on there now it's tiring to ride standing up for very long.
That steel band is a tight fit on there. Yes it can be taken off and put back on but one would need to take great care in the process to avoid damaging the magnets or the flywheel cup. Using a purpose-designed flywheel holder and pushing/pulling tool would remove most of the risk. I was so cautious when I removed one of them I cut it through with a hacksaw to release it and minimise the risk of damaging the flywheel. I lend that flywheel to people who are thinking about taking their weight band off so they can try their bike that way first. None of them have removed their own band after trying that flywheel out first, but some have lightened their BCDE models weight band. Note that the A model already has a light weight band, much lighter than the BCDE models.
In my experience, trail riding an A model is brilliant fun and you can ride the things very fast in single track conditions even with the standard 16 HP engine with standard flywheel, due to their broad power, light weight and excellent handling.
95% of riding over expected logs and unexpected logs is rider weight transfer. The trick with going fast with one of these bikes is to stay on the pegs and stay in one gear and use the broad power. Low gearing gets 3rd 4th and 5th gears close together and these are the gears you use trail riding. Road gearing makes for big gaps between those gears.
Feetup fun- That's good to know information! I was all ready to remove that band and give it a whirl, but sounds like it's not that good of an idea after all. You probably saved me a lot of heartache! But question- I had been running a 12-53 and first gear speed is "too low" to be of much use for trail riding- it takes valuable time to shift thru first, second and you are not moving fast enough to give the wheels any "gyro effect" so there is not much stability until you are moving at about a fast walk at least. So first gear is almost useless. So I put on a 13 tooth front sprocket and that is more "user friendly" my shifting is a bit less often and I'm not needing to change gears as much while reaching a stable speed. Seems like about 10- 15mph is a good starting point. My new boots are stiff enough that you need a definite effort to shift, and that gets old pretty fast on the trail. I'm almost 72 now and that has a lot to do with all this, but do you think a 14-53 is better all around or a 13-53 for single track? Some of the trails here are rocky and fairly steep. I also am looking into Boyesen reeds or anything else that would help me jump a log When- not IF that becomes necessary. What is your opinion on Barkbusters and what tools you carry if you are 20 miles from the truck?
I've just done the opening up of a TY175 intake to take the original reed block out of my TY250, took a while with a dremel but less metal needed to come out than was needed to get the v-force reed block into the 250
What number reeds fit TY250 twinshocks? Boyesen's website show quite different numbers for 74 & 75 which is incorrect as they should be the same part, I suspect what they have for 75 is actually the mono but I can't confirm that
Tony- did you get an answer on your question about the Boyesen reed part number? I am thinking of getting a set of Boyesen reeds for my TY 250 A and hoping it gives a performance increase, but the distributors do not seem to have a particular p/n that is a direct replacement for the OEM stock Yamaha reeds. They mention 3 different models and say they "might work"
Feetupfun- Just looking at your advice about the flywheel weight band- do you know if it is removable and replaceable? I want to try trail riding with the TY 250 A and I'm looking for a little more performance. The heavier flywheel seems to make the motor very slow to rev up and if you are trail riding (not trials riding) and come around a corner and laying across the trail is a log- it takes too long to rev the motor up for lifting the front wheel. I'm fairly certain that my flywheel is stock and un- modified- it has about 6 bolts around the circumference that seem to be holding on a metal band- I am assuming that this is the extra weight that can be removed? What if you simply remove the band entirely for riding single track in the woods?
I'm happy with a 428 chain on my current 250, but the one I'll build as a Majesty is on a 520 setup. The 428 is lighter, remember Sammy Miller went for a small chain to cut down on weight...
Jon v8- I'm running the stock flywheel and I went to a 12 front 53 rear and the front wheel will barely come off the ground with a big hand full of throttle. I'm running a knobby on the rear and the stock carb and exhaust. I want to be able to jump logs if one comes /up on the trail. I have the slow throttle too. TY 250 A model just to be clear. Don't know what I'm doing wrong. Should I be in first gear??
l long time back I read on here that some guys were cutting away part of the left side chain cover to prevent the possibility of the chain getting jammed between the front sprocket and the cases. Has anyone done this mod to the TY 250 A and exactly where is the correct place to cut?
Guys- I think the TY 250 can run either a #428 chain or a #520 chain. Are there any advantages one way or the other? favorite? and why? Best sources? Right now I mostly ride single track and fire roads with a stock 53 tooth on the rear and 12 in the front, but my 53 is about worn out and the chain is about ready to go with it too, so I'm wondering where I can find replacements for all 3 parts if possible. My instinct tells me to stay with steel for the rear sprocket for longevity if nothing else. Any comments are much appreciated!
Ladies and Gents- has anyone recently bought a new rear sprocket for their TY250A - I mostly ride fire roads - bike is still not set up for trials- The sprockets and chain are all worn out-I can start over with either 428 or 520 chain but durability is important to me- I'll be miles and miles from the truck if something goes wrong. But getting back to the question- who is a good supplier in the USA? And part numbers if you have them please!
Just reading the "mail" - Maybe this will help - maybe it won't, but I had some similar problems with my Yamaha TY 250 A.
On the Yam- the flywheel is on the left side and spins Counterclockwise. Yamaha put in a diode between the low side of the coil and the points and the arrow on the diode points to the points if you get my meaning- (cathode end to points) it was added there to prevent the engine running backwards. I put a diode into my 74 and although my timing might be slightly off, it does not kick back quite as much when you try to start it. The setup parameters are slighly more advanced = 3.5 degrees BTDC in my case, but everything else is probably about the same. You might also check the octane rating on your fuel as the higher octane premium fuel will have no ethanol in it to eat up rubber parts or fuel line that is exposed to it, and the flame front lasts a tiny fraction of a milisecond longer than with regular grade fuel.
One thing I found that was semi- critical was that you have to be very certain where the Top dead center is. For this you can either put a tool down the spark plug hole or remove the head and measure with a dial test indicator. Since the piston is not moving vertically at all when at TDC, the flywheel can spin thru several degrees before TDC without the piston moving much at all. I finally resorted to marking the cases and the flywheel with a peen mark on each one that only lines up when at TDC. Having these marks makes it easier to find TDC next time around and saves a lot of hassle. From there you can do the math and divide your flywheel's circumference by 360 and come up with a measurement that puts the flywheel mark back before TDC by the equivalent of so many degrees- whatever your spec says.
That point before TDC is where the points should open. If the low side of the high voltage coil is disconnected from the points circuit and a good quality ohm meter is attached across the points you should be able to detect an increase in the resistance to ground.
That position of the flywheel is critical to the operation,but the points "gap" is also a setting to shoot for.
There is also a very good anti- corrosion and contact preservative I use on every kind of switch contact, points, relays- battery contacts in a flashlight It might be hard to find but it's called "ACF 50" .
So now I took some more of the excess oil out of the gearbox- the level is getting closer to the upper mark on the dip stick with the dip stick loose. Result- starts easier and has slightly more power. Started on 3rd kick instead of the 10th one. This is because the clutch is partially submerged in the gearbox oil. Probably the lowest inch or so of the perimeter of all the clutch plates, so the engine has to spin all this oil out of the way or just churn it constantly. The measurement was taken with the bike on the stand and on the 74 the stand is opposite of the dip stick, so it's still got more oil in it than it needs.
So what are the advantages of a "radial" tire? I know that tube less is not going to work and I need a trials tire to be able to get into some novice vintage events for my 74 TY 250A.
It also has to work with the Dunlop 803 GPF -21 that is on the front end. That tire is a tube type for sure- the words are made into the side wall rubber.
This is getting confusing- I was back on the Chapparral web site and looked up the TR-11 tire there and it said it was "tubeless" again. Does IRC make both tubeless and tube types in the TR-11?
Thanks for the advice, but I don't want to risk tearing up the tire or the rim or me. the rim would have to be modified to make a tubeless tire work and it is so much taller than the front it would look out of place on the bike. I'm just waiting for the vendor to process my refund request. it was their mistake not mine. I just wish I had known about this problem before I ordered it.
That's not a good way to spend $110.00 US - so back it goes- close but no cigar. I'm thinking IRC TR11 in the 4" wide by 18" variety. I guess Dunlop only makes the tubeless rear tires now in the 803 GP T style.
I really don't remember if the first fill was able to absorb a full 1000CC's or not. But now that it has had about 4 drain and refill cycles and none of those was able to use 1000cc's more like 750 would put it on the upper mark. But right now it has about 800 in it and the oil level is about 10mm above the high full level mark on the dip stick. But thanks for the information on the other 70's Yamahas. It's starting to look like a fairly common issue.
I needed the cylinder to freewheel and breathe to check the spark and the control of the kill switch or I would have stuck another plug in there for sure- but thanks for the suggestion.
Feetupfun- Hoing- The only info I had said that the 2 stroke cylinders should NOT be honed with a stone type - hone- as there is a tendency for the stones to get caught in the openings in the cylinder wall. They work fine on 4 strokes because there are no openings to worry about. And actually the 280 grit is pretty fine and does not remove much material at all, so if the cylinder was smooth before it was honed, it will not end up with any aberations from the honing process- and you are only honing for about 30 seconds or maybe 100 revolutions in a push-pull motion anyway. -
And I did not see any darkening of the bore surfaces. So maybe I'm good enough to keep running it- I may go back to a 40 or 50: 1 fuel to oil ratio and see how that works. I might be running the oil too rich.
b40rt- Well - my fault- I was installing a kill switch onto the handlebars and I had the spark plug out to check for spark and I dropped the tiny screw that holds the clamp together for the kill switch right on top of the head! Tinkle tinkle- the screw did not go down the spark plug hole, but almost did. Then I thought - what if something else did go down there? so out of extreme caution (now) I pulled off the head and had a look see- That's when I noticed the markings for the break in. The markings are vertical stripes about an inch wide.
They don't look like deep scratches. Anyway- from now on I will throw a wide rag over the head any time the spark plug is removed.
And on this bike you can have it all back together in an hour or two if you are just pulling off the head only.
What is the standard break in proceedure for a new piston, rings, and a bore that has seen another piston? I honed after the first piston with a 280 grit ball hone, but after 3 hours- the rings are still not seated with about 50% contact right now.
What oil and ratio should I use or should I re- hone the bore and try again? I have .012" ring gaps at the top of the bore right now.
My oil was synthetic Amsoil at 30:1.
There are several contact areas disbursed around the inside of the bore about 1" wide.
What am I doing wrong or what would you change to get the rings to seat fully?
We have to use lanyard killswitches for trials competition here and popular lanyard kill switches are made by Leonelli and Jitsie and have a magnetic action
All my bikes require the killswitch to earth out the LT circuit of the HT coil to stop the motor. These kill switches I mentioned have two wires and either of them can be used to connect to an earth point. It's best to run the earth wire from the kill switch to an earth point on the main frame of the bike, to avoid sending current through the steering bearings, which could otherwise damage the bearings. Most people connect the kill switch earth wire to where the HT coil connects to the frame. Most people connect the other wire from the killswitch to the LT wire near where it connects to the HT coil.
I have the switch between earth ground and the low side of the HT coil where it joins the wires up from the magneto. The problem is that no matter whether the switch is on or off- there is still spark at the plug. I'm thinking that maybe the voltage is arcing across the switch contacts inside the switch when it's open. Does that make any sense? How much voltage would you expect to see on the low side of the coil when the magneto fires?
Update- I did a little more investigating today- I checked the level with the dip stick sitting on the threads - still had about 5MM above the top line on the stick-
I then drained the oil and re- checked the stick- it was now dry to the tip.
I then measured the quantity that was drained- 0.8 Liters.
I took a flashlight and can see the inside of the bottom of the clutch compartment including the gasket at the bottom- there is no obstruction or gasket sticking up into the clutch compartment anywhere near the dipstick.
So I think with the modified drain plug installed, it should be safe enough to operate with 0.8 Liters on board. The dipstick is happy anyway.
I will keep an eye on the oil level and report any news I come across, but since the dipstick goes dry when the oil is drained, I feel pretty confident that the dipstick is giving a valid reading.
Took all the lights off- need a good way to cut off the power to the coil- The switches I have are both momentary two wire switches that mount on the handlebars. I think they are meant to ground out the pulses to the primary side of the high tension coil. What has worked for you? Details please!
it's possible that the gasket is the problem- I noticed that the gasket appeared to be a non- Yamaha part because there is a sort of watermark name printed into the paper that did not say Yamaha or anything close to that. It's also almost a black color rather than the greenish paper that the Yamaha gaskets are usually made from. And yes- and just going from memory here the dipstick still shows a higher than normal oil level after the oil is drained- not for long, but for a few minutes anyway. Since then I have switched oils to something called "clutch saver" 10W30 and now the oil level is barely above the top mark. ??? Unfortunately, my camera memory stick is no longer functional and I lost the photos of the gasket when the clutch cover was off. The modified drain plug is still doing service in the bike now too, so that is still a factor in this mystery. If I get a chance, I will take the cover off again and have another look- the problem could cause severe damage if the dip level was high only because of the gasket.
TY250A Flywheel question...
in Yamaha
Posted
motovita- I try to stay on the trails pretty much, so not a lot of brush busting on my rides, and the full wrap around brushbusters seem like overkill - more weight and expense. Unfortunately in my area there are very few trials events within driving range. I can't find a seat option (Trials type seat pan and cushion that is designed for trials for this bike. ) Also my suspension system is pretty stiff for clearing logs- seems like it's bottoming too easy without moving much and the rear shocks are also not moving much- makes for a fairly rough ride. - can't find any help for either one of these problems!