lemur

Titanium is the ultimate if you need to ask the price you can't afford it material. Cota dogbone is a super simple design, you could sketch it out on a table napkin and if you can machine 2 holes with accuracy it will work.

There would be a lot more demand for Cota linkage dogbones, more of them out there and the expensive stock part gets smashed easy.

If you are looking to source raw Titanium you might want to try Titanium Joe out of Kingston, Joe rides EM trials bikes and has access to a supply of used Ti material.

Lots of potential causes, a leak in a pressure line is just as likely as a blockage, does it have a battery or capacitor, does it need a bigger battery or capacitor. Fi pumps can usually be checked for performance by powering them up to an external power supply and measuring the volume of output over time.

Fuel injected? sounds like low fuel pressure at startup

Oil change costs me about 7 bucks 🤓 (roughly the same cost as one litre of race fuel) and UDT works good even in sub-zero weather ⛄ like we are about to get here very soon. If the clutch drags because of the hydraulics just raise the idle a little, that works. If your clutch makes noise and the oil drain looks cloudy that's water, water happens a lot when you do deep water crossings or the engine insides are exposed to condensation, such as riding in winter 😎 or power wash your bike.

Here is the best reference:

You are going to get a lot of different answers but the best oil to use in a 2-stroke motorcycle transmission is the oil that you can change more often. 10w30 is multi-grade oil which is 4-stroke engine oil, your engine is 2-stroke and the oil never sees engine cylinder operating temperatures, it does have a wet clutch and gears and for that I use the same thing I use in a farm tractor construction excavator which is also full of gears and wet clutch plates, UDT hydraulic oil ISO46. Others will have other recommendations but this is what works for me and it is cheap enough to replace frequently and that does more to save your transmission parts then expensive oil left in there for a long time. Only two things can pollute your transmission oil; water and dirt from internal parts wear.

Optical inspection instruments, borescope or fibrescope inspection might reveal a problem without splitting the engine casings. 🤓

Your transmission has 3 shifter forks, shifter forks are made from soft cast material and prone to wear or bending. Shifter fork 1./3. Shifter fork 2./4. and Shift Fork primary. If only some of the shifts are a problem but not all, shifter forks is what I would inspect. When a shifter fork experiences wear there will be an accumulation of metal particles in the oil when you drain it, (not likely to be magnetic) make it habit to dump your old transmission oil into a clear glass container and inspect it for fine metal bits.

Those are calculated numbers, what does a measured compression test show & Is it hard to turn the engine over even on the down stroke, or only as it reaches TDC? If this is a new or escalating problem on a used engine; remove the exhaust header pipe to do a partial visual inspection of the piston rings and barrel to make sure nothing is seizing the piston.

I always buy trials bikes in pairs and have no problem keeping at least one of them running, you need that second bike to 100% identify a sporadic failing component, that's how a dealer would fix it and keep the service cost reasonable, just swap assemblies until the problem goes to the other bike and now you know what parts to order.

I ran high test pump gas in 4RT's for nearly 2 decades and never had carbon deposits anywhere near what your plug chop shows, occasionally added 50% Sunoco GT260 for better performance and they definitely run better and cooler with higher test fuel, but never found 98 to be a requirement. Based on my mid winter riding experiences the fan should cycle for short periods even in sub-zero riding temps. ... race fuel here costs about 7$ per litre so motivation to run cheaper pump fuel is considerable.

😎 Good to see you finally upgraded from running diesel fuel 🖖

I can't even imagine how a 4RT engine could be making that much carbon, unless the sump is pumping engine oil into the intake or the air filter is over saturated with filter oil and it's sucking that into the intake, or an intake valve guide compromised. Does your engine eat oil?

Next test I would do is hook up fuel delivery to the carburetor and move the float lever part #70 up and down with my finger, observing how well the valve allows fuel to flow into the float bowl area and to stop the fuel flow correctly when you raise the lever. Works just like a toilet, if you can fix a leaking toilet you can fix a carburetor.

Did you check the fuel filter? Part #53 in the parts diagram http://ducatimeccanica.com/dellorto_diagrams/phbh_l_diagram.jpg ... part #61 is the seal others were questioning.

If you change the way the airbox access cover bolts on, you are far less likely to snap the rear fender in the typical fashion. Secure the airbox cover to the fender even with glue works and then bolt the fender to the bike with only the front bolt and 2 small zip ties at the rear part of the frame, then when you crash the entire fender will come loose instead of breaking the fender into two. That Bosi front kit looks like a copy of the stock Montesa fender and bracket and the half length rear tail looks like a copy of a TRS 2 piece fender, seen them live and they look like the wrong fender bolted on there.

For the front fender you are not limited to buying Beta, other brand front fenders will fit and a Montesa front fender bracket is a good start point. Beta rear fender there is a way to change the air box cover bolt and reduce breakage of the stock rear fender plastics, you make the airbox cover attach to the plastic fender instead of bolting to the frame, that reduces breakage of the rear fender plastics.

Squirt about two ounces of fish glue into the tire before you insert the valve stem, inflate the tire and roll it around to see where the glue starts to leak out, now you found the leak and sealed it too. Also works great to seal tire studs that poke through the tire a little too far. Fish glue is high tack fast dry glue commonly used in woodworking, it 100% reactivates by adding water, non toxic and easy to clean up. Unlike commercial tire sealant, fish glue hardens into a flexible skin that will help to make the tire stick to the rim and not slide on the rim. I know it sounds strange but it 100% works.

OEM HONDA TIRE LOW PRESSURE GAUGE part # 89301-HA0-772. 👍👍 doesn't need to read accurate as long as it reads consistent.

Decompressor defeats engine braking, at least it did on a BB34 Goldstar 😎 that was the only bike I rode with a manual decompressor.

Where do you plan to ride (what terrain do you typically have available) ? Montesa 4RT excels at many things but the nearest dealer for me is 4000km away, so parts support and buying new bikes is not one of them. PGM-Fi fuel injection is the best 👍 4RT handle far more planted where most 2T bikes tend to handle more lively, the 4-stroke engine wins if you ride at continuous sustained speed for long periods, 4RT' thrive on really long steep climbs where you need to peg the throttle and leave it pegged. Throttle control between the 2T and 4T is the biggest difference, what works on one is not right for the other, 4T engines don't like to be blipped, 2T engines work best for short bursts of insane power response, the Montesa has a 5 plate clutch to deal with heavy use of the clutch.

Today I was helping a friend track down the source of the same symptom, bike ran and started poorly when it got hot. On disassembly it turns out the piston is badly scored near the exhaust port and small bits of piston literally welded itself to the cylinder wall. Bike is a 2022 model with only 150 some hours on it. We didn't see anything to account for the damage so far such as foreign material and the damage is limited to where the exhaust port opening is. In retrospect the piston damage would have been visible to inspection by removing the exhaust header only.

I think my entire body is going arthritic but riding seems to help 🖖 my arthritis hurts most after periods of stagnation, seems to go away when I'm riding, comes back in a hurry when I crash and can't get up. Treatment plan is to ride more, crash and stagnate less. ... now if you can tell me how to get out of the truck after a long drive and not feel like a 100 year old man in need of a walker 👍 I'm considering glucosamine supplements because it did seem to work for my dog. Curious if anybody has had success with that?