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Post by insideright on Jun 23, 2011 15:43:04 GMT
Afternoon Chaps, Some advice from the experts please- Recently had a re bore and a new piston fitted carb jetted correctly im finding that after a short amount of miles the plug is oiling up change it and away we go. Would the dealer have set the carb up for a rich mixture while im running in With the view of me taking it back to him to re adjust once the running in period is over Everything i have looked at tells me that the plug should be a brownish colour and that what i am looking at every 60-80 miles is exactly what it shouldnt be. Look forward to the solution
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Post by dave1967 on Jun 23, 2011 20:52:16 GMT
Hi Sounds like you have the wrong main jet fitted, you really should get it sorted before you do some damage try going down a size or two.
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Post by colin4255 on Jun 30, 2011 14:22:13 GMT
Plug should be a kind of mid to dark chocolate brown colour ideally. Not too light. Having it run richer while running in is not a huge issue, but you should get it sorted. Depends on what sort of barrell/piston you have. Is it standard? Is it a big bore kit? Do you have a sports exhaust? Is the carb standard?
Main jets are dirt cheap - couple of quid. The size is stamped on them. 110 - 112 - 114 etc. Standard PX125 is I think 108 or 110. Whatever you jet is now, maybe try one a couple of sizes smaller - say if its a 114, try fitting a 112. BUT they may also have screwed up the fuel mixture. There is a screw at the back of the carb. Turning it in will weaken the mixture, and out will richen it. This is a nightmarre to get right if you do not knw what you are doing. Typically, the mixture screw is usually set between 1 3/4 and 3 turns out depending on what jet etc you have.
Might be an idea to take it back to them and get them to set it up a little better for you. Even running it slightly richer while running in wouldn't mean the plug fouling up.
I am running in a PX125 witgh a DR180 kit on it and I am simply using a 3% petroil mix instead of 2%, but the plug isn't fouling up and the thing runs fine
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Post by bryno on Jun 30, 2011 16:20:57 GMT
Do you mean oiling up? (wet) or is it just black (and dry)?
If it's just dark I would not worry about it until you have finished running it in and can open it up, once you do that you can fine tune the mixture, being rich in the short term will not do any harm and you may find once you've run it in that on full throttle it is actually fine and just a bit rich at the bottom end..
Mix screw should be around 1 1/2 turns out, but this will not make much difference to the mixture as soon as you are on throttle, it only has an effect on tickover and the first little bit of throttle.
Personally, I'd not change the mix from standard 2% mix unless the installation instructions specifically say to do that.
More oil = Less fuel in the chage, which is what cools the motor, so it runs hotter and you are more at risk of a seizure...
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Post by colin4255 on Jul 1, 2011 12:36:28 GMT
Thats interesting about the mix. Seems I have been given some bum info by colleagues - I was told it was better to increase the mix when running in to avoid the chances of it nipping up? Thanks for the heads up.
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Post by dave1967 on Jul 1, 2011 22:05:14 GMT
Hi All Just to get it right Oil burns hotter than Petrol the more oil you are burning the hotter the engine will run 2% to 3% may not sound a lot but think of it as 50% more than is recomended.If you are running a kit in such as a DR kit then the standard autolube will deliver the correct amount of oil, a malossi or Pinasco may require the autolube disconnecting and mixing yourself when filling the petrol tank. Run the engine in properly and check all the cylinder bolts regulary over the first 300 miles and with the correct jet you wont have any problems, the air mixer screw on the side of the carb wont make the slightest differance to the fuel-air mixture once you pull away it only adjust the mixture whilst on tick over. I have found that DR kits run fine on a 115 main and pinasco 116 but that does depend on what exxhaust is fitted. If the jets to big then the engine will cough and splutter and wont pick up, drop down a level and try again I normally find that you can get there within three changes.
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