Bm1200

I use an extended one off eBay listed for a vm26. May not quite be the right profile as the adjustment is a little sharp. Works ok but there is nothing easy about adjusting it unless you have long thin heat resistant fingers.

http://www.mikuni36.com/Images/BSR36-carburetor.jpg http://www.carbrescue.com/pdfs/mikunibsr36.pdf These aren’t exactly the same as the Beta carb but are very similar. I don’t remember seeing anything like it in my carb and there is nothing obvious on the diagrams. If it fits in the recess over the idle mixture screw it could be what was left of the anti tamper cap after some one drilled it out. the diagrams show the build up of the carb needle. The spacer is a thin washer that allows you to set the needle the equivalent of half a slot.

They are listed on the CMSNL website https://www.cmsnl.com/honda-cota-4rt-2006-6_model32013/cover-tappet-adj-hol_12351nn4000 not cheap even before shipping

Mine sounded like that when I set the clearances wrong, the decompressor opens valve twice when turned by hand or kick speed. I set the clearance when it had slight lift on the decompressor cam therefore way to big when it was on the base circle. I didn’t use the tdc bolt, thought that should ensure you’re in the right spot. I’d work out where the valve is at max on the main and decomp cam and turn the crank 360 and set the valve clearance there. It’s so much easier with the engine out.

Plastic screws are god but may only solve part of your problem. I have the later air filter cover type and found you need an M5 screw for the lid otherwise you can still snap the mudguard. You can run an M5 die down an M6 screw which saves ordering 2 lots of screws. I also cut the lip of the mudguard where is meets the air box. like other people say you can use tie wraps but it wont save you if the air filter lid is bolted down. I buy M6 x 16 screws on eBay from China take ages to come but cost next to nothing. Nige

Hi Dean Lock down has given me the chance to do a bit more maintenance, so while the engine is out I popped the water pump shaft out and took the attached pic. The seal surface is visibly polished but no detectable groove or edge you cam feel after two years, probably around 80 hours, Grease was still present with no signs of leakage. Re-greased with red rubber grease for another year.

Hi there I found the best trick with your old 4t is to take the master cylinder off the bike lower it and tilt it so the air can go straight up hill. You will need to push the piston with a screwdriver and it would be useful to have a spare hand to open and shut the bleed nipple but it does the job in about a dozen pumps. Nige

Sadly all the seals will need changing as they will have swollen and eventually split, might be ok with the pipe but it will need to be flushed. lots have people have made the mistake the other way by putting Dot 4 in mineral clutches.That generally works for a week before the seals swell up and split. BMW motorcycle forums are full of tales with bikes from about 2010. This mistake is less common because not so many people have mineral oil in their garage to make the mistake. I have first hand experience because my Nephew was sold Mineral oil to go into a Peugeot braking/Clutch system that should use DOT 4. First the clutch went light then stopped lifting fortunately it made it undriveable before it stopped the brakes working. The cost was enough to scrap the car. Nige

I’ve got a 2012 300 4t with a 2015 guard with the filter access hole. Fits perfectly. Nige

I have a 2012 300 4t which uses a pair of 6004 2RS in the rear 42mm dia. and a pair of the smaller 6904 2RS in the front 37mm dia, some apparently use 6004 in the front. 2RS means rubbing seals in each side. 6904 are the same as 61904 for some reason Nige

No not a plug chop but they take no time to go black, the hotter plug stays a better colour. It seems modern fuels dont really go the old fashioned brown colour.

I have the same problem in the UK with my 2012 300 4T 120 Main Mine came with 27.5 but tried 22.5 to get the mixture leaner ended up with 17.5. Needle currently in top groove, plug still just as black, it uses no oil so it is not likely to be that. I wondered if it was really rich or if the plug was not hot enough to self clean so put in a harder plug 6 in place of 7 that read a bit leaner used to have a lot of back firing with all the jets but got round that by putting a lighter spring in the overrun enrichment valve. Not sure if it had the right spring in but it seemed very strong. Nige

I had never heard of the silicate issue. Must admit I was going for metal compatibility having seen some pretty horrible corrosion/erosion of some high magnesium alloys but will be going for silicate free in future. Mine leaked it’s water into the sump didn’t help that the vent hole was blocked with degraded grease which is why I used red rubber grease which seems to have great water resistance compared to other greases I have used. Will post another pic next time I get the shaft out. Nige

Hi Dean Have you found the 4t engine manual online, it shows the locking bolt in the crankcase. I didn’t bother , with he mass of the crank I was able to undo it with a sharp tap and did the same to tighten it. I couldn’t find a torque any where. I haven’t seen a high capacity pump for the 4t but don’t have any problems in the uk climate. I popped the shaft out after a year and stuck some more grease in. With the ordinary nitrile seals there was no signs of wear. The more recent manuals show this as a 40hr service and 80 hr seal replacement. Will have another look in January.

A better pic of knackered shaft

No problem the thread is normal so anticlockwise undoes. I got my seals from simplybearings in the uk size 10 x 18 x 4 inner bearing is HK0608 outer bearing HK1010 ( still in the spares box) Special tool sounds a bit grand now I look at it

Had the seals go on my 2012 300 4t. this is what I did lay bike on side remove weather pump cover remove circling and impeller used home made tool to unscrew water pump shaft. The benefit of having the bike on its side is the drive sprocket doesn’t fall into the engine. I dropped a small rod in just to keep it still until I put the new shaft in. Mine needed replacing because the seals had worn deep grooves new shaft cost £80 ! lever out seals I bought new bearings but they are tricky to get out. I decided to leave them rather than fail to get them out and damage them in the process. the seals go front to front. Ie the open spring side on the inner seal faces cam chain tunnel and the outer is open side to the water so that the pressure improves the sealing force. I bought beta seals but they seemed like hard viton that may increase the shaft wear. I put in some cheap nitrile ones that are fine after 2 years. I put red rubber grease in between the seals. I notice that this is now shown as an annual service item since 2018. The tool I made was dead simple. Get an M8 nut and drill it out 9.5 mm cut a slice off one side to end up with a D shape 7.5mm across. I welded a bit of metal to close the straight edge of the D and filed it back to a hex. Tap it on stick a socket on it and give it a sharp tap! Hope this helps Nige

I am new to trials and not ridden many bikes but always found the rear brake weak on my 2012 300 4T. I spotted that Jitsie do one with a larger tip that sticks out further. Being a cheapskate I made an extension to the tip which comes out about 20mm further. I found it a lot better, with the original tip only the inside of my boot is on the pedal so the harder you push the more your foot rolls off. With the longer tip the force is through the centre of the boot and it seems to be much more effective. I may try and make another tip with the same extra width but moves it forward and effectively lengthens the lever. I could just spend the money but it’s not my style.

If you have a welder stick a bolt or nut in the middle, tack it in and drive the bearing out, warms the hub nicely to get the new ones in too.

Hi the US Beta site has lots of manuals to download. https://betausa.com/content/SUPPORT_PDF's/2011%20Evo%20125-290%202%20stroke%20owners%20manual.pdf that one has the torques for the rear linkage. Nige

Got a 2012 with the later mudguard with the air filter lid. Plastic bolts and trimmed the lip off the underside. I bought m6 bolts and managed to run a 5mm die down one to use for the air filter lid. Only snapped the rear bolts so far. Would have been on second or third by now.

Bleeding clutches is a lot more difficult than brakes, you can spend ages pushing air back and forward. If you un bolt the slave cylinder from the side of the engine it is much simpler, the piston goes full travel and bleeds just like a brake. When bolting the cylinder back on It will just push the piston back as long as you haven’t taken too much slack out at the lever. If you can’t bleed it like that the you have another problem. Hope it does the trick