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Oil won't hurt the throttle body. The fuel injector is after the throttle body and that is where fuel residue would start to be apparent, if anywhere. Race fuel is a very aggressive solvent if you have been running poor quality fuels and will be going through the injectors. Crankcase ventilation is critical to preventing oil going places it should not, like past the intake valve seals for example. Spray solvent can dissolve the blue silicon insulation inside the main electrical connector, use only air if it gets water condensation in it. If any flame gets past the 4-stroke valves the filter could ignite unlike the 2-stroke 315 model, hence the addition of a flame screen is required. .

200 Euros labour plus parts sounds quite reasonable to me and even cheap if they have to source or make a special puller. Do they know what's involved?

Didn't really find it with my google search... I'm in Italy, BTW. I tried to find a mechanic willing to do it... some say they won't open the engine unless it's for a total check of all the parts. Another guy asked for €200, not sure how long it takes but seems a bit on the steep side, maybe? I should also take the engine out and pack it to ship it to his shop (and of course have it picked up after the job).

Just an update on this. I’ve had my 4rt bought new for about a year. The inside of the throttle body does in fact need cleaning. I’ve found the inside of the body, around the butterfly value had a light coating of oil. This is either air filter oil residue sucked from the filter, blowback from the engine (I guess that’s why the air filter has a fire proof mesh) or both. I easily cleaned this out with carb cleaner. As a note DON’T DO THIS! The solvent in carb cleaner affects the throttle body air pressure/temp sensor. It was a bitch to start at my next trial until I flushed enough air through the throttle body. Use specialist throttle body cleaner, which is designed not to effect the sensor.

I had an identical issue with my brand new 301RR. On laps 3&4 of a trial, where I wasn’t stopping to look at sections, the gear change was terrible and at times the bike felt locked into one gear. I couldn’t find neutral with the engine running while waiting at sections and if I stopped the engine, I couldn’t start it again when it was hot. I adjusted the tappets which cured the hot start issue (these really do need doing after the bikes first run in and every 6 months after). I did the washer adjustment on the rear of the clutch basket which massively improved the gear change, especially when the engine was hot. The washer needs adjusting every few months and I’m yet the find a way of stopping the free play (it’s only about 2mm) but it massively affects the gear change.

some pictures of the damage

Any pictures of rhat Jon Bliss mod?

Hello my name is Lee and I live on the Big Island Hawaii. I just purchased my first Bultaco model 92 Sherpa T 350. I bought it as a basket case for 500 bucks with some new parts . Seat, grips, tires, tubes, and exhaust and a powder coated frame . The guy I purchased it from brought it over from Oahu. He purchased it from a guy who worked at the Pearl Harbor naval station ship yard. I got to meet the original owner when I was stationed at Pearl Harbor as a dock master. I used to own a Bultaco Metrala 250 El Tigre and a Matador mk4 250 5 speed when I was a teenager. This should be a really fun project.

Yes it's not easy but are you saying you can't find where to buy the special puller from?

Uhm... gotta say the videos of guys pulling the cush drive with a handmade puller didn't really make me think it was easy. I tried to get in touch with a few mechanics here, specialized in old enduro bikes, but for now still no luck. Not really too excited at the idea of doing it myself, this bike is definitely way different from what I usually wrench on...

Perhaps it has something to do with it being your first post here? Perhaps it has something to do with Kenda being sold on the website (albeit with a spelling error) you promoted above?

Hey, I finally opened the 301 engine and my friend the mechanic was right piston was worn quite badly. No big damage to te cylinder wall just needs a light hone and an new piston and rings. Will fit a new distribution kit too now the engine is in bits. Bike has been well serviced and i use good full sysntethic oil. Maybe previous owner didnt serviced it enough?

Seems legit 🤣

If you ride in mud or slick conditions stick with Dunlop or Michelin. If never touching mud then ride a clapped out used one of the above. Using an ibex or Shinto is cool only if you need some rubber between the rim and you. Riding in Australia once was great but traction was every where. Riding in mid west us, Central Europe and north east us has me loving tire engineering from the pros. I use irc on only tubed rears because the bead wants to roam and not stay where it's told. --Biff

I think you can get a clear float bowl for that carb, makes it easier to diagnose 🤓

Start it in neutral is the obvious one as Pro clutches have a tendency to drag no matter what type of oil or ATF you put in. If the bike has a KEIHIN PWK 28 then take the Jet metering block off and clean the tiny holes you see of any gunge then put a new jet block gasket in before putting it back on. Make sure the jetting is not too rich as it just soots the plug if you are not thrashing the motor regularly causing bad starting/running. In my experience the standard plugs are better than the NGK platinum in the 125 and they are better with a bigger gap like 0.7. Do not over oil the air filter and 80:1 in the tank is plenty of oil , you do not need more to be safe unless you are running it in a trial with lots of road work. Take the reed block off and put some new standard reeds in to make sure its all as it should be and be scrupulously clean while doing all the work and make sure gaskets seal properly.

Triad, if the primary drive crankshaft sprocket has a cush drive, then it is an easy job to change the crankshaft seal, but you need to buy a special puller for the cush drive. These pullers are available from vintage OSSA parts suppliers in the UK and USA. Buy a primary drive cover gasket and crank seal holder gasket while you are at it.

Hello guys, sorry to resurrect an ancient thread... I have an Ossa engine requiring new crank seals as it's drinking gearbox oil. I'm kinda skeptical about doing the job myself as I never worked on such an old bike and I don't have the pullers. Is it hard? What kind of pullers do I need? The engine should be from a late 70s Pioneer, has the coarse teeth levers and runs, so the Motoplat rotor is good and has good compression. I'm in Italy, can't find a shop willing to tackle the job for me.

There always seems to be a focus on fuelling and I recognise there's been some success with playing with it but I don't know what it is particularly but I like the idea of weak spark being a culprit. Especially in this case where the OP has gone to great lengths to prove it (apparently never solving it tho). I fully understand the fuelling has to be right, and 2 strokes are renowned for clogging jets etc so I get where the focus on fuelling is coming from. But the fact gassers are so well known for poor starting even on very new machines would point to something else at least not helping. Went to the Reg Bowker yesterday and watched in awe as the riders jumped on their bikes after refuelling and with just one kick we're off again! Even gassases! No magic dance or superstitious routine. So it is possible to achieve.

Assuming there is not an electrical problem, making the starter jet richer can help. Does it have a Dellorto? If so, they have replaceable starter jets. When I did not want to wait for jets to arrive for my old TXT321, I just enlarged its original #60 starter jet hole from 0.023 inch to 0.028 inch (making it approximately a #70). Much easier to start! Figured I had nothing to lose, as I could just solder up the hole and re-drill to original size if it made things worse. The jet number is the approximate diameter in millimeters, so a #60 would be about 0.60 mm in diameter. When I drill a jet, I obliterate its original markings so the next guy is forced to measure. But I also always supply a full set of note with any bike I sell.

In the 5 years since this post went cold, has there been any development on improving poor starting?

Had my first "cold" ride today. (It's not actually cold, maybe 8°C) but i did get both hands drenched within the first 20 minutes. Anyway, heated grips are absolutely amazing. I went with this kit from splat shop https://www.splatshop.co.uk/heated-grip-kit.html I binned of the resistor and switch for high/off/low And just wired it into my headlight wiiring instead of high beam. So now i just use the pre-existing switch on the handlebar. I rarely ever ride at night so thats no issue, but it's just the swap of 2 spade connectors to return headlight to normal.

https://youtu.be/9TH3osNOdBY?si=QsjThBvRpJ9lP

Ok another trial last weekend which was harder. I was pretty switched on for some of the first lap. Then got progressively worse. Think I'll try the kit but need to get past Christmas and cash flow issues. I could just take money from family account but I expect the wife to keep to a budget for play money account so I probably should. . .