dwayne

Quick update on the OKO carb, I felt it a bit dull to pull away so I followed this advice:- It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving. Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Before you start the jet testing, Install a fresh plug. Warm the bike completely, and shut it off. As already stated, start with the pilot circuit. Turn the air screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idling. Turn the air screw slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the air screw for the best response. Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet. Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the air screw slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn. The air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day. The full article is here https://thumpertalk.com/forums/topic/347305-is-your-two-stroke-running-rich-read-here/ Basically I turned the air screw out ( about half a turn ) until the revs were at their highest then turned the idle screw out about a turn to lower the revs back down to a good tickover, it now pulls like a train right off the bottom. I was surprised how much difference it made. The above is the same advice for a Delorto carb or any other 2 stroke. It helped me I hope some one else benefits too!

Hi, No markings on the package at all, its working fine, it only has two piston rings just like a cr 250 piston. I sent the cylinder and the piston to langcourts so it was guaranteed to match. Works fine, no issues. https://www.sadboyracing.com/online-shop/dirt-bike-parts/#cc-m-product-6770788011 The racing one i got is out of stock but they still have the three ring piston kit which I can't vouch for, but there are few options.

Buy a 26mm oko carb on ebay £29.99, works great, get a 50mm foam filter too, £10ish. It's an easy fix. The problem with the dellorto's is:- they have no overflow, if there is a problem with the floats or needle valve etc, fuel leaks into the crankcase, that makes it hard to start with poor running etc.

Try the radiator caps from japanese cars at a scrapyard, they worked fine on mx bikes.

Hi again, Just to say the bike is now up and running, I got a 26mm oko carb from ebay, it runs much better than the worn old Dellorto! If any problems occur I'll let you know!

Search for '315 pistons', on this forum, all the links you need are there.

Hi all, I got the new piston, it has only two rings with it, there are no identifying marks or makers name on it. Wrapped in a soft grease proof paper in a plain box. I have sent it and the cylinder to Langcourts, i am waiting for them to get back to me with a price for fixing the cylinder and matching it to the piston. Fingers crossed.

I don't know if they are in stock at splatshop or not, but they can get pistons size A,B OR C, for about £80, no rings to go with them. They are trying to get rings in. http://www.splatshop.co.uk/montesa-cota-315r-piston.html in stock here https://www.sadboyracing.com/online-shop/

Hi, I have just bought a 99 315r which needs a piston, i did not realise that this would be so difficult and expensive !!! My motocross days (long gone) presented no such issues, 50 for a piston and 30 for a rebore !!! I found this lot https://www.sadboyracing.com/online-shop/ who do piston kits they are not cheap, I was warned of the quality of the rings on the standard kit so I bought the racing piston kit at €245 !! They only take paypal and the exchange rate is not at all good. I don't have much choice so have had to bite the bitter bullet and pay up, The guy at splatshop said they are doing their best to source piston rings, they do have pistons at a reasonable price just no rings at the moment. Rings can be bought from https://jbanyeres.com/en/home/2684-kit-3-original-piston-rings-for-montesa-cota-315r-all-year.html €155 for three rings which will match splatshop pistons, still an expensive kit I do not know anything about the quality of the rings, the pistons from splatshop are Honda so no issues there. Hope this helps. Alec