What the... gearbox acting up

Shop deals on ebay
Advertise with us
Find deals on amazon
Mini Dirt Bikes & Pit Bikes Forum

Help Support Mini Dirt Bikes & Pit Bikes Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Flarry

Flarry

Certified MR Member
Joined
Feb 20, 2007
Messages
2,447
Reaction score
0
Location
Adelaide
Well my new engine is on its 3rd tank and today I was trying to beat my old time on the track, theres a corner I allways come up to fast in 4th then quickly put it into 3rd and use engine breaking to slow me down enough for the corner, pin it around the corner in 3rd then get back into 4th straight after, I was coming up to this corner and I put it into 3rd, let the clutch out and all I heard was clicking and no engine breaking, I went off the road and crashed into a fence.

3rd works allright now, did it just not engage that time? I let the clutch out pretty fast and I was going pretty fast. Im super cautious because this is my new engine, broke the gearbox in my old engine and if this one breaks I wont be riding for along time!

Is anything wrong with my gearbox or should I have just slowed down before I put it into 3rd and tryed to match the revs better?
 
yeh id say you just hit nuetral when you were pinning it...
suck and hurts when you hit the fence but you get that sometimes ;)
 
That would have been pretty funny. Just wondering, you seem to give these engines a pretty good beating and your riding daily. How often are you doing oil changes?
 
I check the oil everyday before I start riding and top it up if its not full, and I change it when it starts to get black. Should I change it on a regular basis? Like once a week or somthing?
 
if your riding it pretty hard, it really should be changed every 2 or 3 ride max,

some say after every solid days riding....

IMO well b4 its turning black!
 
Change my oil in the race bike every 2/3 meet.

Change my oil in the pity every 2/3 thrashing.

Maybe change the oil more often.

As for the 'click' and no engine braking, sound like you have a slipper clutch :p
 
pitmaster said:
if your riding it pretty hard, it really should be changed every 2 or 3 ride max,

some say after every solid days riding....

IMO well b4 its turning black!
Click to expand...

Whats the actuall science in changing the oil? I thaught the reason you should change it was because it gets thin and stops working, how long does it take to get to that stage? Whats the reason for changing it every 2 or 3 rides?

Is that homebrand 15-40 oil ok to use? Its alot cheaper!
 
Agreed with pitmaster. 4 strokes run much hotter then 2 strokes and require more frequent oil changes. Honestly, if your riding daily and thrashing your bike every ride you should be doing oil changes at least two or three times a week for increased engine life and reliability. The oil thins out when exposed exposed to heat. So I wouldnt go any longer then 5 hours on the same oil. I would use a quality brand oil if I was you.
 
quite a few racers use cheap as cheaps car oil, and change it after every days racing, $13 for 4 litres is almost 5 oil changes,

i personally use Valvoline car oil, the base XLD cause it has less additives.

its $14 for 5 litres, which gives me 6 changes, ive being using it from day one in my engine (12 months now) its never had one single engine problem, and gets a kaining every weekend, and after work week nights,

doesnt use a drop after a full days riding, and i change it after every 2 full days riding,

so this bike vs car oil is debatable IMO, i just cant justify spending $13 litre on motul and dumping it every week,

My cousin has the 2007 YZF250 (white edition) and has to change it after every ride!
 
Last edited:
oil must be changed erery 3 rides to clean out the engine they dont have a filter like a car.
 
i had a 2 stroke 1982 yz50 i gave it a solid days thrashing about 15 times while i had it and never had any problems. how often should you change the oil in a 2 stroke?
 
thats just gear box oil, so not as regular, probably on that thing three times a year
 
they do have some filtration for the oil... ;) oil sling which itself should get a clean

i hardly ever change my enginge =) when i run it in it got a good 3 changes but havnt changed it since.. havnt had any probblems tho ;)

im my mate old engine i dont think he changed his oil for a good 6 months if not more and it keept running as hard as it ever did ;) till it blew up from too much kaining and revving =P
all fun XD
 
Flarry said:
Well my new engine is on its 3rd tank and today I was trying to beat my old time on the track, theres a corner I allways come up to fast in 4th then quickly put it into 3rd and use engine breaking to slow me down enough for the corner, pin it around the corner in 3rd then get back into 4th straight after, I was coming up to this corner and I put it into 3rd, let the clutch out and all I heard was clicking and no engine breaking, I went off the road and crashed into a fence.

3rd works allright now, did it just not engage that time? I let the clutch out pretty fast and I was going pretty fast.

Is anything wrong with my gearbox or should I have just slowed down before I put it into 3rd and tryed to match the revs better?
Click to expand...


That's EXACTLY why you're busting your gearboxes ...... pit bikes have wide ratio trannies that take time to engage the dog lugs due to the big differential in speed between the main shaft and counter shaft so you have to give your engine a good quick rev BEFORE letting the clutch out in a lower gear ....... if both shafts aren't spinning at the same speed the dogs will skip past the locating slots and if you force them in you risk snapping them off .

Jap MX bikes have close ratio gears so they shift quick and easy because each successive gear isn't spinning much faster or slower than the gear you're shifting out of ....... you only have to drive a truck with wide ratio gears to see that they'll crunch if you try to shift too quickly whereas cars can be shifted pretty quickly ....... especially a 4 or 5 speed ..... but they'll still crunch if you can shift lightning quick ........ most revheads who stuff their car gearboxes up do it by banging them down and using engine braking . On upshifts the helical cut gears force against a solid thrust face but on down shifts they move in the opposite direction and force against circlips which eventually get hammered out of their grooves allowing gears to clash and smash teeth off ........ race cars use straight cut gearboxes which are too noisy for the street but can tolerate rapid down shifting and heavy engine braking ......... learn to use your brakes better ......sudden forced engine braking without matching the revs spot on will soon take it's toll on your pitty's tranny ......

Incidentally I've used Valvoline XLD in worked XR's for years and the tranny (32 year old 5 speed Yoshimura close ratio with under 8 mm wide cogs) shows virtually zero wear ...... the ends of the dogs look like the day they were made and there's no rub or wear marks between the engagement slots of the counter gears - can't say the same for the Honda primary drive crank gear or clutch basket gear though but they are still in pretty good shape for 33 year old parts ............. Rub marks on the sides of the female gears between the slots or polished or worn dog lug ends means whoever has been riding the bike is a turkey and can't shift or use a clutch properly ........ :p
 
great work cactus jack!! i definatlly leant something there =D

yeh i always give her a squirt when im dropping it back a gear.. match the revs

hell yeh im liking oyu 32 year old 5 speed =D they definatlly dont make things like they used to...
 
Yes they're made out of a super tough forged steel alloy (probably Kryptonite soaked in Superman's piss) ........ the gear teeth still show the hob marks on the wear surfaces whereas the Honda parts show wear and are polished like chrome on the thrust faces ....... I paid $275 for it brand new in 1975 ....... a new XR was only around $425 at the time so today you'd be looking at $1500 or more for a similar quality tranny .....
 
so what ur saying is i can use valvoline xld instead of motul wich costs me 13 bux a litre
sweet
 
Cactus Jack said:
That's EXACTLY why you're busting your gearboxes ...... pit bikes have wide ratio trannies that take time to engage the dog lugs due to the big differential in speed between the main shaft and counter shaft so you have to give your engine a good quick rev BEFORE letting the clutch out in a lower gear ....... if both shafts aren't spinning at the same speed the dogs will skip past the locating slots and if you force them in you risk snapping them off .

Jap MX bikes have close ratio gears so they shift quick and easy because each successive gear isn't spinning much faster or slower than the gear you're shifting out of ....... you only have to drive a truck with wide ratio gears to see that they'll crunch if you try to shift too quickly whereas cars can be shifted pretty quickly ....... especially a 4 or 5 speed ..... but they'll still crunch if you can shift lightning quick ........ most revheads who stuff their car gearboxes up do it by banging them down and using engine braking . On upshifts the helical cut gears force against a solid thrust face but on down shifts they move in the opposite direction and force against circlips which eventually get hammered out of their grooves allowing gears to clash and smash teeth off ........ race cars use straight cut gearboxes which are too noisy for the street but can tolerate rapid down shifting and heavy engine braking ......... learn to use your brakes better ......sudden forced engine braking without matching the revs spot on will soon take it's toll on your pitty's tranny ......

Incidentally I've used Valvoline XLD in worked XR's for years and the tranny (32 year old 5 speed Yoshimura close ratio with under 8 mm wide cogs) shows virtually zero wear ...... the ends of the dogs look like the day they were made and there's no rub or wear marks between the engagement slots of the counter gears - can't say the same for the Honda primary drive crank gear or clutch basket gear though but they are still in pretty good shape for 33 year old parts ............. Rub marks on the sides of the female gears between the slots or polished or worn dog lug ends means whoever has been riding the bike is a turkey and can't shift or use a clutch properly ........ :p
Click to expand...

REALLY?? That would make sense, broke 3rd gear on my old old engine, probably because I allways used to go really fast in 4th and put it straight into 3rd to slow me down, hope I havnt done much damage so far!! I'll allways remember that now!! My dad was telling me to do this, has driven alot of trucks and stuff and knows all about it, it was allways in the back of my mind but I didnt think I was doing damage. I allways try to slow down a bit and not just let clucth out straight away.

But when I do this does it damage the selector dog? Because thats the part I broke my old engine.

Thanks for the info!!
 
You must log in or register to reply here.

Latest posts

Back
Top