mcman56

The lower legs can be modified to accept standard size bushings.

With light oil and teflon coated bushes in the lower legs, I find the stock TY175 forks to work pretty well.

My Beta once ran the same exact way. It would idle nicely and doing tight turns was fine but if you tried to rev it up, it sputtered rich. I had left a rag in the air filter after washing the bike. You could inspect the air box. https://www.frankmxparts.com/rebuild-repair-kit-MK-BSR33-79-Mikuni-BSR-33-carburetor-2008-2022-Beta-EVO-300-4T-Trial IIRC, that model carb is also used on a 400cc quad. If you search the model number of the carb you should find what else it fits.

Interesting comment. Then, what would be the 4t technique for a basic double blip over a log? I went one tooth down on the front sprocket and that feels pretty good.

I have a 2018 300 with black throttle tube. It looks just like the 2T throttle. Is a slower one available? I have a 2016 Beta 300 4T standard model and the throttle has much more resolution for small blips, maybe 100% more resolution that makes throttle control much easier.

I compared riding position on the Beta 4t to the 4RT and the handlebars were 1" further forward on the 4RT (compared to the pegs). I think this put more weight on the bars promoting the nose feel heavy. 30 mm riser additions brought them back to be more like the Beta. It also looked like the forks had not been serviced in a long time and fresh oil made them perform much better. With these two changes, it feels much better and the nose dive feeling is gone..

Did you measure how much squat was in the back? I added some spring preload to the forks plus more rebound damping to the shock and it feels better. Still, the shock feels stiffer than the forks. This bike has a fork compression damping adjustment on the bottom of the left fork leg. The manul implies it is only effective when the forks are bottoming.

Not as pretty as yours but this should work. Thanks for the details. Do you have a recommendation for a home use hobby level TIG machine?

engine braking - maybe but rolling on and off the throttle in first gear, my beta feels like it has more engine braking

Engine performance is very strong. This is in first gear, clutch out, double blip. I'm an old guy with damaged hands so more clutch usage would not be a good solution. To rephrase my question, what can make a bike nose dive on the back side of a log. I have not been on a modern or vintage bike that did this.

I got out for a ride on a new to me 4RT and it is quite different from my Beta 300 4t. This is a 300RR version, 2018. Power is much sharper than the Beta but it seems like power is cut much quicker than on the Beta. The front wheel really slams down on the backside of logs, even a small 10 inch diameter log.. I tend to double blip most any obstacle. I'll do a second blip when the tire is on the front of the log or on top, chop the throttle, bikes roll over and set the front end down. This 4RT just drops the front wheel like a rock hitting the ground pretty hard on the back side. I'm wondering if this is the way fuel injection works or could it be something else. Could it have less flywheel weight than the Beta for less run on? I put the electric start kit on but the flywheel is still very close in weight to the OEM flywheel so I don't think the starter has an effect. Simply bouncing up and down on the suspension seems OK but I wonder if too little sag, too much compression damping or too little rebound damping makes the rear tire slam in causing the front tire to slam down. Or is the Montesa just like that.

Has anyone successfully replaced the drive chain tensioner bushings? Mine is a 2018 and appears to have a solid bush but the replacements (with the correct part number) arrived as a compressed split bush. They also look a little too large. When I look at them, the chance of getting them installed, round and fixed in the swingarm to work with the tensioner seems small. Has anyone done it? Does it work? It does not look good.

I did heat the hub but was not careful with the old bearing. It is marked SKF France.

I disassembled the second bearing and the inner race is cracked. You can also see stress marks in the ball area of the matching outer race so maybe the cracked race allowed things to move around. I did use an expanding anchor to try and remove one of the bearings so possibly could have cracked the race but that would not explain the stressed out race. I have never seen a crack like this before.

Per my measurements, the non counterbored spacer is the correct width for this particular hub. I have ordered a new one and will verify its size. That brings up the question of how the counterbores got pressed in. I do not think an inner race could be moved 0.016" without destroying the bearing. Even if it did not destroy the bearing, I would expect it to fail immediately. The ring of interface between the bearing inner race and spacer is only about 1 mm wide. I would like to understand before installing all new parts and having it lock up. I have high confidence in my measurements but they may not be perfect. I could get an outside mic on the hub and used a depth mic for the bearing counterbores. They are rather thin and have a corner radius so not easy to measure but the number I found was the same width as the bearing. Maybe something is wrong with one of the bearings. To get this apart, I had to rip the cages from one bearing to remove the balls and inner race but I can take a look.