Virago 250 excessive backlash

[Knuckle Buster]

Does anyone know how much slop is safe to have in these gearboxes? I checked the clutch basket and clutch components and everything looks perfect. There is not even a single spot worn in the basket and steel plates and clutch linings are good and fit very well without slop. The problem was there when I got it, it runs, and shifts perfect, but it has a Super Lot of backlash in the output shaft.

The original chain was worn when I got it at 5,500 miles so I replaced the chain, rubber cush drive, and installed 17/42 sprockets. It helped the cruising at 55 but the awful slack/play/backlash or whatever yall want to call it is still there. Every gear is the same. It's not in the chain, or the chain adjustment. The front sprocket fits the shaft like a glove but in any gear I can turn the shaft with two fingers without any resistance over a quarter turn each way before it stops. On the stand with chain removed the shaft will turn over a quarter turn each direction before it hits the end of the slack. It doesn't matter which gear it is in, the slack is there.

Does anyone know how much slop is tolerable before facing a failure on the road? It has so much slop somewhere inside the engine case that it actually breaks traction temporarily in 1'st or 2'nd if I'm turning in to my uphill drive and have to release the throttle to avoid a bump and give it slight throttle again. That's how much slack is in there somewhere.. it'll absolutely slug that rear when the throttle has to be released to slow then even with the slightest twist of the throttle it'll slam again off the backlash. But none of this is from the chain or rear cush drive.. all that is brand new. It is somewhere in the engine/transmission case itself.

*Edit. I should also say that that when parked in gear, any gear, I can roll it back and forth freely a couple feet each way before the it reaches the end of the slack each way. The front sprocket and shaft are moving the whole time until it reaches the end of the slack inside the case each direction.

I've only ridden it about 300 miles since I got it because I'm worried this may not be right and it may fail. My other bikes in the past did not have this feeling, but I've never had a Yamaha 250 so I don't know if it's normal, semi normal, or just isn't right.

[DGA]

Without knowing that motor directly, first check that the front sprocket nut and spline drive is ok. After that, I would remove the clutch cover and put it in gear and attempt to replicate the problem by moving the rear wheel or moving the bike. Watch for something slipping, my guess is that it is not inside the gearbox but is on the primary drive side.

[Tom Boyte]

Knuckle Buster.
That's weird. I have owned a new XV250 Star and a used 89 Route 66...Neither has any of the slack that you described (meaning I can't roll it a foot or so either way while in gear). Don't sound good. You might want to ride or trailer it by a Yamaha dealership and "pick their brain". It doesn't mean they have to do the work to fix it. Keep us in the loop with what you find and good luck.
Tom

[JrZook]

There will always be quite a bit of "slack" or "backlash" when turning the output shaft on these bikes as the dogs and dog engagement slots in the gears have quite a bit of clearance in them. All my 250 boxes seemingly have a lot compared to other bikes. Not the nicest or smoothest setup.

[Knuckle Buster]

There will always be quite a bit of "slack" or "backlash" when turning the output shaft on these bikes as the dogs and dog engagement slots in the gears have quite a bit of clearance in them. All my 250 boxes seemingly have a lot compared to other bikes. Not the nicest or smoothest setup.

Ah the dog ears. Makes sense. I work on vehicles but never cracked a bike case in half before. I was dreading the thought of going deeper in to investigate. Other than the slack it seems to be a really good dependable bike. I'm second owner, I got it from a lady who bought it to learn on then it sat in her garage quite a while after she bought a harley. She only put 5,500 miles on the little 250 but it was used on open road and interstate with factory 16/45 sprockets. So I was worried something may've been over spun when she told me she forced it to do 77 on I-40 to keep moving with traffic. I removed those sprockets right away and changed them to 17/42 before taking it out on the hwy. I still won't take it out on an interstate myself even with these sprockets because it still revs pretty hard above 60. I'm used to a 84 Shadow with overdrive so I baby this thing

[CX Rancher]

for mine, I can roll about 6 inches fore and aft in 1st gear with the clutch OUT. I have 40,112miles on the original power-train/drivetrain

not feets by any means.. dango.

[Knuckle Buster]

for mine, I can roll about 6 inches fore and aft in 1st gear with the clutch OUT. I have 40,112miles on the original power-train/drivetrain

not feets by any means.. dango.

Yours sounds about right for the design of the gears. But I've decided after having a look at the complete guts of a transmission out of one of these for sale that there isn't enough clearance in these dogs to allow 92 degrees of backlash/free play like mine is doing. My output shaft turns 92 degrees left to right by hand before coming to the end of the play. I ''guess'' maybe a staggered dog that sits in the center of the slot may've been broken off at some point before I got it and might be allowing much more free play than it should? Or maybe it has multiple parts inside that are badly worn causing enormous slack combined. I haven't a clue without breaking the case I reckon, but I'm almost positive it isn't right. It also has a loud whine from the gearbox that increases with speed. I may have to investigate before long. I haven't ridden it much because none of my atv's or bikes have ever had internal slack quite like this one, not even if a chain was ready to fall off they've never felt this bad.

I appreciate the replies. I'll post my findings sometime later on after I find time to look into it. With twin granddaughters almost 3 and a 1 year old grandson we're raising there isn't much time to spend in the shop. What time I do get, my lawn mower seems to get every bit of on 7 acres. But papa's don't give up, I'll get this thing opened up one day and post what I find.

[JimL]

A note about constant mesh transmissions, beginning riders, and new GM pickup truck rear differentials.

OK....bet that got your attention! Anyway...these things are sometimes related. First, a little explanation: when you buy a new Chevy/GMC pickup truck they warn you not to tow anything or carry heavy loads for the first 1500 miles. What is happening is the metallurgy process is now using the owner as part of the "hardening" step for the gears.

Why? My best guess is that it saves a little manufacturing cost and generally works out fine.

Steel is not a solid, as most people believe. It is actually dendritic crystals in a tangled matrix. For a clearer picture of the structure, just remember that Ivy is a dendritic plant....tangled but not bonded. Under tension, the crystals jam up and become very strong. Under impact, they slip into tighter "packing" and compress. That is why the head of your chisels mushroom over when you use a hammer on them.

Many years ago, in a former trade, I worked on a lot of rider training motorcycles. When new riders kept them lugged down (on brand new bikes) the backlash in the transmissions would open up rapidly. If the bikes were ridden normally for a few thousand miles, they worked much better as rider training bikes. We used to see want-ads looking for used 250 Rebels and similar that already had miles on them with experienced riders. Those ads were posted by rider training schools.

The total lash is nothing more than stack-up of small tolerances, added together. The problem is that it is a tiny bit, at every tooth, dog, spline....all added up. It is too expensive to fix, part by part, because it is all of them...evenly.

One more note about steel (iron): the dendritic crystal structure is why you cannot successfully paint 50-100 year old cast iron engines. The oil penetrates all the way through the iron and you cannot get it out.

That characteristic is also why iron makes wonderful cylinder liners and great skillets for cooking up bacon "just right". It is also the reason why my family and friends have had to retire some great old vintage car racing engines. Once the iron is fully saturated, it is about as strong as wet sand!

[Tom Boyte]

JimL,
Thanks for that explanation. Very interesting.
Re: Cast iron engines. I have one in a 1957 Cushman Eagle scooter I bought when I was 14. I'm 71 now and still ride it on occasion. I have replaced the rings and inserts twice and points and condensers several times in all those years but it still starts and runs well after a couple of kicks. looks like it will outlast me.
Tom

[Knuckle Buster]

Thanks for the replies. I've read them all and a few days ago decided to put it on the road and give it a chance. I've ridden it 700 miles in 4 days and am getting used to it just being what it is. I just use 2'nd gear climbing my long gravel uphill drive and also use 2'nd all I can when barely moving in traffic to keep a constant pull so I don't feel the slack back and forth. It's not as big of an issue as when I first rode it. I was used to a 1984 Shadow 700 shaft driven that I rode several years to work in all weather before selling some time back. It had a tight feel even when I released the throttle and opened it again in any gear at any rpm just for kicks. I guess the little 250's have greater tolerances which is ok if that's how they were designed to be. After actually sitting on it 700 miles since the weekend I'm better trusting it. I really like how cheap it is on gas, I got 200 miles out of a tank once riding carefully on a non stop haul. When I got back to the hills here about 150 is all I could get but still that's good IMO. The hills are steep and twisting but being only 132 pounds it does very well for a 250.