mcman56

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.

From your answer, I take it that the spacer should be a simple tube so I ordered a new one. It seems odd that the issue just showed up now. I use a torque wrench. It has over 200 hours on the bike. Maybe an original crush at the factory plus tiny moves at the axle tightening finally made it tight on the axle. I took some measurements and the spacer without counterbore is the correct length. The pressed in counterbores are 0.016" deep each. It seems odd that a bearing would take that kind of side load for a long time. The bearings are pretty small. The shoulder on the inner race is particularly small in area where is presses on the spacer.. The spacer does look like some kind of extrusion and I was tempted to make one of 6061 but I would have to order material for that too. Do you think the manufacturers all make their own wheels? Most of the bikes come from a small part of the globe so I wonder if they all get their wheels made at tahsame place.

Is the front wheel bearing spacer on a 2016 Evo just a simple tube or are there countersinks on the ends. The pics I see on line look like simple tubes. Would anyone know the exact length? Mine has countersinks on the ends that match the inner ring and sort of a bulging ring on the ends of the ID. Could this be correct? See pictures. To pull the front wheel from my Evo for a tire change, I had to use a hammer to get the axle out of the wheel. I never had to do that on this bike before and there is no corrosion. The bearings were crunchy feeling but there was no place to use a driver so I had to remove the inner race from one side to drive the bearings out. These are the original bearings, made in France. The bearings were greased so not a rusty failure mode. The spacer still will not slide over the axle from either direction. It does not look like the bulges on the ID were machined. It sort of looks like the countersinks on the ends and the bulges were formed by crushing the spacer but is that even possible? Strange

Curiosity made me look and I found this. It suggests that there is/ was a racing head available. However, it shows the racing head making more top end power and from my understanding more compression should make more low end while choking off the top. Is yours a 280 or 300? Could someone have put a 250 head on a 280/ 300 or a 280 on a 300? I would expect that to drive the compression way up. Does the engine knock (pink?) a lot when running. https://www.ossa-efi.com/home/engine/heads I had a Rev3 270 that was hard to kick and had very sharp power right off of idle. Adding 1 mm of base gasket in addition to the original made it easier to kick while softening the off idle power. It was a common practice, easy to do and easily reversible. I was told that someone used to make head spacers for Gas Gas to do the same thing so I once made one for a 250 Techno when trying to make it so my 100 lb daughter could start it. It was simply a 1/16" piece of sheet aluminium cut to match the head/ cylinder interface. One side sealed with the OEM o-ring. The other side was just flat surface to flat surface with a little silicone. IIRC, it was still too hard to kick but ran leak free long after it was owned by someone else.