Sprockets - Does new bike have the wrong ones?

[Lou Ranger]

Just bought a wonderful XS400 Thurs. The last owner did everything to make it as good as new. All I have to do is ride it - which suits me fine for now as I am 61 and just started up again last fall with an sr250 (after 36 years).

I am wondering if a previous owner might have changed the sprockets to increase acceleration and lower-speed performance.
If the revs are a hair above 3,000 while moving in any gear, the engine will accelerate without stumbling. Below that it demands a downshift.

I am happy to keep the revs over 3,000 - but in top gear, going 60 mph (98 kph) the engine turns at 6,000 rpm. I'm constantly wanting to shift into 6th gear - but it isn't there. Does that relationship between revs and speed sound normal/stock?
If not, then what should the revs be in top gear at 60 mph?
If it is normal and I therefore have stock sprockets, could I nonetheless add a couple of front teeth and subtract a couple of rear teeth? I find myself preferring to cruise at 50/80 (5,000 rpm) instead of 60/98 to avoid the 6,000 rpm buzz.

Thanks.

 

[drewpy]

you might have one tooth less on the front (standard xs250)

standard is 16, I have a 17 and can't go any higher due to clearance issues.

6.5k @ 70mph

9.5k @ 110 mph.....i wish

 

[eric123]

Count the teeth to be sure...

 

[Lou Ranger]

It's awful cold outside today - may take me a while to get those counts.
I did confirm that I have a 5-spd not a 6 (from the cover plate showing 1N2345), but I seem to have an xs400 "Maxim" which apparently has more cams and one less gear - though I suspect that top gear is likely the same for both.
Do you consider 6k rpm at 60 mph (98) to be excessive? I am reading about people at 4800-4900 at 55 mph. That would be nice for how I am riding.

 

[bentwrench]

Lou, I ride that bike too. It's in pieces right now, so I'm not sure what my RPMs are like on the highway, but I remember them being high (Bike tops out at about 95mph, as much because I run out of power as gears.)

It's easy enough to check the front sprocket teeth. Remove the shifter pedal, and then take a phillips screwdriver to the 7 or so bolts. That will give you access to the sprocket for a quick count. 16 on the front and 35 on the back is stock (I believe...)

 

[Lou Ranger]

Thanks bentwrench, I rarely get up as high as my age so I'm not too worried about running out of power. I weigh 155-160 so it sounds like I could go up a tooth on the front if I only have 16 now (or maybe 2 if I only count 15). When it stops snowing, I will venture out to count. Sure was a short summer this March

 

[bentwrench]

I like that this bike runs out of steam up there. My last bike was an SV650, and a Bandit 1200 before that, both of which hit well over 200 kmph. I figure I'm likely to live longer, and become a better rider with less power. Every bit of momentum counts now!

 

[Lou Ranger]

No ride today - maybe will count teeth later

 

[Lou Ranger]

The road to hell .... good intentions.
I have 35 teeth on the rear sprocket and an unknown # on the front.
Not one of the Phillips screws holding the cover will budge, but I can turn the driver hard enough to feel that I'm on the edge of stripping each one. If the penetrating oil makes no difference by morning, would heating them with a soldering torch help?

 

[ThePsuedoMonkey]

Phillips? Shouldn't the screws to the covers all be 5mm hex?? I guess that could just be how the maxims do it, but that seems crazy to go from hex to Phillips... Regardless, I always use an impact screwdriver on stubborn screws. You can pick one up for ~$10 at pretty much any automotive shop. Also, it seems to me that penetrating oil never works very well on aluminum. If all else fails, you can use Drewpy's trademark: weld a nut to the top of the bolt (or screw, I guess).

 

[bentwrench]

Yeah, Maxims have Phillips head machine screws.

Lou, I'd pick up some PB Blaster at Canadian Tire if I were you. Stuff works wonders. And yes, the cross will give way and shred if the bolt isn't nice and loose. And to make things worse, the PB Blaster needs to get into the threads, which are quite recessed on the cover (the oil needs to get past the thickness of the cover, and into the body of the engine.

But then, that's where all the fun comes, right? If you do shred a head, you can rebuild these soft screws by hammering the screwdrivers. I just go slow and steady, with lots of downwards (sideways in this case) pressure after a good blast of PB Blaster.

 

[bentwrench]

Oh, and of course, use the biggest phillips that will fit. The more metal that touches between the bolt and the screwdriver of course, the more force you can bring to bear on the threads.

 

[Lou Ranger]

Should we be doing a commercial for Robertsons at this point or would it be lost on the rest of the world?

 

[bentwrench]

I remember a (possibly apocryphal) story about border guards calling Robertson screws by their own name: crowbar screws. Whenever they needed to open a crate from Canada secured by Robertsons, they'd just call for the crowbar instead.

 

[jayel]

not phillips head screws, they are JIS screws (Japanese Industrial Standard) a Phillips screwdriver will bottom out in a JIS screw preventing full engagement of the screwdriver flutes, this is why it's so easy to cam out those screw heads (to be replaced by allen heads), cheap solution is to grind off the tip of your phillips doesn't take much or buy JIS drivers, a hand impact driver comes in handy too

 

[226dark]

final drive on my bike is 16 and 37. At 60 mph the tach reads 4600. At 70 mph the tach needle is magically dancing and bouncing around and seems to be at 5500-5600 rpm's.

It has 480 miles on it now after fresh rebuild and the first miles on it were more like 5600 rpm at only 60 mph. The more miles I put on the less work it had to do and was glad for that.

Can the screw be pulled out with a 5/64" left-hand drill bit? Should pull it right out. Or regular drill bit then # 1 extractor.

 

[bentwrench]

JIS. Good to know!

 

[Lou Ranger]

The local tool supply had a hand impact driver for over $50 and nothing else.
And they never heard of JIS so I may file down a spare Phillips tip.
Got some heavy duty Blaster (more than a penetrating oil) and will see how well it penetrates overnight.
In the meantime it runs beautifully with an unknown number of front teeth.

 

[ThePsuedoMonkey]

$50!!! I grabbed one from autozone for $10 last month!

 

[bcware]

Few people have heard of JIS; the response you got is normal. Ordering a driver online is your best bet.