I have been a trials rider since 1974. My 1st trials bike was a 1974 TL125. That was also my last 4T trials bike. Since then I have owned and ridden only 2 strokes and at least 10 were GG 300’s. My current bike is a 2023 GG 300 GP. I love it and at 68 years old, it is way more capable than me. I have considered the switch before, but always go with the 2T - lighter and probably more power. However, I am not nearly as concerned about a few extra bike pounds at this point, and the sections I ride are no longer filled with major obstacles.

I recently acquired a beautifully restored 74 TL125. I am thinking now might be the time to get the most state of the art, current example of a 4T trials bike. A 2027 301rr when they become available. A cool couple of bookends.

I would truly welcome the thoughts of anyone who may have made a similar switch before.

Anybody….? Thoughts?

If the distribution and dealership representation was better here, I would be riding Montesa again. The Cota is far more settled in the suspension, not as lively as many 2T bikes and the 4RT thrive on revs with smooth throttle control and lots of clutch abuse, great bike for hill climbs and deep mud. They don't cold start in serious cold winter weather unless you have a heated garage or build a fire under it, small concern for most. After about 3 or 4 years you will need to learn how to adjust valve clearances very accurately.

Riding a 4T is totally different but great. We've had 4t's for probably 11/12 years... did recently by a TRS just to see if we could be tempted back from the dark side but although the TRS is light and nimble I think we'll stick with the 4T's. You could consider the beta 4t. less complicated. No F.I, ECU, Throttle body, no expensive pump in the tank. Slower idle speed (4RT idles at 1800rpm). I'm a rubbish rider, but had a 4rt which I nearly scrapped due to intermittent throttle body issues. Got it fixed then moved onto Beta 4t's... never regretted it, so much so my son bought one. Had them for probably 8 /9 years now..

4Rt's are lovely bikes but if they do go wrong (not often, granted) then its a pain to try and trouble shoot unless you have a spare bike to swap parts over on as I found.

omg Honda PGM-Fi is light years superior to the CV carb on any motorcycle, it has one screw to adjust, the idle and it never misses a beat.

Beta CV carb has what? 2 chokes, vacuum fuel tap, vacuum throttle lag and a vented float bowl just like a toilet tank works.

... was it water or condensation in the connector to the throttle body? is fixed easy, open it and blow the water out.

Edited October 24Oct 24 by lemur

Thank you for your thoughts. Not sure what I will do, but will continue to ponder.

20 hours ago, Kschwartz said:

Anybody….? Thoughts?

When initially changing from a 14 Beta 300 2t factory to a 16 Beta 300 4t, I struggled with full lock turns. The 4t felt a bit abrupt just when the throttle slide lifted so it tended to push the front wheel. It took a while to adapt. The 2t was fairly smooth up to mid range when it started to produce lots of power I did not need and it could get me in trouble. By comparison, the 4t felt fluffy on top.

I later moved on to an 18 300 4rt. I was told the Beta 4t and a 300 4rt were very similar but it was not my experience. (also rubbish rider) The Beta had a much softer throttle response in the lower rev ranges so required less precise throttle control. This could be good or bad depending on your taste. Probably because of the softer response, it hooked up quite a bit better in low traction situations. I can't quantify but the 4rt feels bigger which could be a plus or minus based on your size. I believe it is about 7 pounds heavier. The 4rt frame feels much more rigid and transfers more shock through the handlebars. At 70, I have had surgeries on both hands plus forearm problems so am very sensitive to the shock forces. It is not the fork tuning as the Tech fork is quite plush. I ended up making rubber handlebar mounts to compensate, like CRF250. I like low idle speeds so the higher idle of the 4rt is annoying. The quietness of the Beta is nice. Initially, the 4rt felt like a real handful and it took me about 10 hours to get comfortable on it .

Maintenance wise, the Beta 4t carb is much more difficult to get out compares to the Evo 2t carbs. Then, you almost have to drop the Beta engine to get to the valves. Valve adjustment access is infinitely easier on the 4rt. Oil changes are much more difficult on the 4rt. Oil filter access requires removing an engine side cover. It has separate engine and transmission oils. The recommended 4rt trans oil is $50 per liter. The 4rt rear brake is much better than the Evo rear brake.

5 Montesa 4RT bikes over 20 years I only used ISO 46 hydraulic transmission oil in the transmission/clutch casing, never had a lick of transmission or clutch problems and the oil cost 7$ per oil change, change it frequently because there is no filtration on the transmission, the thing that destroys the oil is water from condensation or pressure washers. ... don't use pressure washers or swamp the bike and your oil will last longer 👍

Did the ISO 46 change the clutch action? I started with the recommended oil but am now running Dexron VI. The Dexron changed the clutch action a bit and I had to adapt my clutch timing. It is difficult to tell but I think it engages later but quicker plus it removed a little drag. It must be a little thinner in the operating temperature range. A more progressive engagement would likely be better for me. I'm wondering if Dex/ Merc would be slightly thicker.

Working on excavators and farm tractors and operating them year round I noticed they are just huge heavy duty versions of a trials bike transmission. I run shorty levers so the clutch engagement changes just with that change, clutch progression is the result of hydraulics. I think ATF is perfect for automatic transmissions, my trials bikes all have one of the most simple standard transmissions and organic friction plate clutch systems ever produced. The ISO 46 works even in sub zero it is considered all-weather. Water swells clutch plates and lowers the burn point of the oil in the clutch. Burning the oil between the friction plates is what causes the carbon glaze that builds up on a cooked wet clutch and that comes from improper combined clutch & throttle control.

The ISO or SAE or AGMA measure is the viscosity measure relative to temperature, the rest of what differs is what additives are in the oil to make them suit a particular task.

If you had to do a 45 gallon oil change in an excavator or farm tractor at the cost of some small package oils being sold in bike shops, you would go broke real fast.

On 10/25/2026 at 12:24 AM, lemur said:

omg Honda PGM-Fi is light years superior to the CV carb on any motorcycle, it has one screw to adjust, the idle and it never misses a beat.

Beta CV carb has what? 2 chokes, vacuum fuel tap, vacuum throttle lag and a vented float bowl just like a toilet tank works.

... was it water or condensation in the connector to the throttle body? is fixed easy, open it and blow the water out.

I'm not a road rider, I just mess around on a trials bikes so my experience is limited, but as the question was asked by the OP & I thought I'd share my experience and thoughts.. I will never notice the difference between a carb and FI in terms of performance and I would respectfully suggest nor would most other clubman rider...FI is brilliant when it works and I'm sure somewhere in that black box its been programmed to give the best performance.. It appears many manufactures are now going to FI, but I suspect that's more to meet emission regs rather solely to provide the best performance for the club rider. In my experience, when it starts to play up its a pain to diagnose the issue without a second bike to swop parts and if your unfortunate to have an issue its not going to be a cheap fix. When trying to sort mine, most of the loom was corroded, Black wire corrosion all through the earths, most of the loom was replaced. When the ecu was opened up just before launching it into the nearest bin there wasn't any visible issues with it. I agree there are a number of elements within the carb that could effect its operation, but other than a blocked jet due to stale fuel or a bit of debris they rarely go wrong, just like a the FI system in 99%of bikes, but carbs can be easily stripped and cleaned ready to go again whereas a FI system can't...The other issue we found is the idle speed on the Montesa.. its around 1800rpm, any less and the bike wont start, whereas the beta is around 900rpm and it drops lower and still pulls whereas the Montesa will stall and we found we had to use much more clutch which was also relatively switch-like compared to the beta...just my thoughts and experience...