Yamaha YZ250F

[j bjork]

Here is the faster run, should be about 105km/h on the gps I guess:

About 20kw and 6800rpm..
Maybe I should give it more fw, I only have 70A now.
Not that I have much use of going faster

 

[j bjork]

I noticed a problem last week after I was out riding:

I thought that cant be good, and remembered I had seen a new hub on an ad some time ago.
Found the ad and bought it:

But I also tested how it was to weld, and it welded up just fine:

The wheel was to big for my lathe, so I left it with a friend.
It tured out it was to big for his lathe too, so he milled it instead:

I did hope for a little better finish, but at least I didnt pay for it
It was also time for new bearings, they had never been changed before.
I think they lasted this long mostly because of the covers on the wheel spacers, but it seems hard to find new ones with those covers.
So I made my own:

I first made one of ABS, but it broke when I tried to press it on.
These are of TPU, printed without problems

I was riding again today, and noticed the bike got noisy.
Back in the pit I found this:

I decided it was time to change there and then, luckily I had a used one in better condition

I was about to change chain and sprockets, but I am out of new front sprockets..
I have ordered some, but still waiting for them.
After todays ride I noticed that the chain is pretty much done as well:

 

[amberwolf]

It's a good thing you ride so gently in such clean conditions so the grit can't wear things down and torque can't break stuff. :lol:

 

[j bjork]

Yesterday when I was riding I broke the front fender instead:

That's unusual, I have only broke one before when I rammed some trees..

The bike stopped ones for me, and wouldn't start until I stopped and stood there for several seconds.
It also didn't start up very good at first.
At first I thought it must be a motor position problem or similar, but then I remembered I saw some voltage difference at first when I stopped. I think it was cell 9 reading low. They all look ok now though:

Some difference but not too bad. I'm thinking it could be a balance wire that is starting to brake off where it is squeezed at the cable lug. I think this battery has done about 100hours, so it is not impossible.
If the bms sees a big voltage difference and cuts there could defiantly be some problem when the bike starts up I think.
I guess I just have to test the battery again and see if the problem comes back
This track was perfect for a test like that though, 8-9km of rocky misery

 

[j bjork]

Broke a damn tire again:

I didn't notice until I got home again though, mousse can be really good sometimes
I guess I better change the tire right away, in my experience those holes get bigger fast

 

[harrisonpatm]

Yesterday when I was riding I broke the front fender instead:

That's unusual, I have only broke one before when I rammed some trees..

The bike stopped ones for me, and wouldn't start until I stopped and stood there for several seconds.
It also didn't start up very good at first.
At first I thought it must be a motor position problem or similar, but then I remembered I saw some voltage difference at first when I stopped. I think it was cell 9 reading low. They all look ok now though:

Some difference but not too bad. I'm thinking it could be a balance wire that is starting to brake off where it is squeezed at the cable lug. I think this battery has done about 100hours, so it is not impossible.
If the bms sees a big voltage difference and cuts there could defiantly be some problem when the bike starts up I think.
I guess I just have to test the battery again and see if the problem comes back
This track was perfect for a test like that though, 8-9km of rocky misery

I had an issue like that last week with ANT BMS: loose wire that the computer interpreted as one cell being 2v and the next being 5v, and shut down.

 

[j bjork]

I was racing today, first heat went fine.
Then at heat 2 it started running rough and cutting out. If I stopped and released the throttle it was fine again.
It continued like that several times. I thought it might be the reverse switch, like if it got connection, then not, connection again etc.
Then after lap one the problem went away.
Luckily I was logging, but as usual it doesn't seem to show much:

I think I caught 2 cutouts here (the flatlines), it shows 0 fault as usual. But I think it is interesting that I get -400pA soon before the cutout. I could have been braking, but the brake is set to max 200pA..

 

[j bjork]

A bit of an update on this issue, I also posted it on 3shuls facebook page, and Hackey asked me for the log.
I hoped he would be able to see something, but he only replied that there was no fault code (I knew that).

Anyway, he seemed to think it might be an throttle issue. I opened up both gas and brake throttle to have a look:

Both were potted, so I couldn't really see much.
I changed both, and disconnected the reverse.
I also took off the cover over the hall sensor in the motor to check that there was no moisture, and it wasn't.
Today I was racing again, and had 2 cutouts.
No rough running, just clean cuts that I had to release the throttle and stop the bike for it to take throttle again.
(not turn off or anything)
It seemed to me as a overcurrent cut, but I shouldn't be close as I run 1200pA with 1400pA max with 100% setting.

But I ran a 75% profile, so only 900Pa. Or at least, that is what I thought..
I was making a new post at 3shul, and took some screenshots when I saw this:

Find 2 faults in this picture
It is the other way around, 1200pA protect, and 1400pA max..
I suppose it has worked mostly as I have ran the 75% profile (1400x0,75=1050pA, so should work I suppose)
I wonder how it has happened though, I dont think I have touched it for a long time.
Can it have changed itself?

 

[j bjork]

I connected reverse again before riding again today, but suddenly I got the problem with the bike running rough and more or less not moving forward. It didn't help to stop a few seconds this time.

I did notice that I could reverse just fine, but not go forward..
After disconnecting the reverse button again the problem was gone.

So I suppose it was two problems, but when I got the reverse button problem it also often caused the over current problem.
I hope it is all fixed, now I only have to change some bearings and work on the suspension

 

[j bjork]

I have been struggling with the reverse problem. Hackey suggested to add a ceramic cap between ground and signal to filter. From those I had he suggested a 100nf (the biggest) but then I had a little rough start. He then suggested a 1uf cap. I didnt find any, so I tried a 10 or 11uf instead, but still got a little rough start.

I had already taken the button apart and cleaned it, so I thought it would work anyway without cap as it has done until recently.
But today I was at a race, and it started again
I had to stop and disconnect the button, but at least I have made it easier.

If 100nf (0.1uf) and 10uf doesn't work, and gives similar problems, could it really work with 1uf? In that case I will of course order some.

I had a scary crash today at the race, on a fast sand uphill with loose rocks (cat sculls) I got one of those front wheel hits that just sends you in another direction. I then hit an old stump after a tree, and got a root in the front wheel somehow
I went flying, and more or less landed on my head, in the sand luckily and not on a rock
Both the bike and me was surprisingly unharmed, I think the front fender got hit pretty hard judging by the "white stripes" in the blue:

It doesn't show very well, but there is a line from left to right, and some front to back.

Have some straiting out to do on the handguards too.
It sure is time for some suspension work:

I have had a bump in the inner pipe for some time, I just fixed it temporary with filler..
"My" suspension guy seems to think he can push it out, so I hope he is right.
There is some scratches too that I have sanded down as good as I could..

I used to have these blue protector rings on both legs, but I have lost one some time ago.
Now a piece of the leg itself have fallen off obviously, that probably happened today

Took some sag measurements before I took it off:

In the rear it is with about 10mm preload on the spring.

 

[bananu7]

"My" suspension guy seems to think he can push it out, so I hope he is right.

The walls on the inner tubes are steel and surprisingly thin; it could very well be possible. Still, with the way you ride, those parts are pretty much wearables. It's good that sourcing spares for those bikes is easy as they're so popular.