Surfrat25 Posted December 3, 2013 Share Posted December 3, 2013 Hey Everyone! Hope everyone had a good holiday! I have a 1979 Yamaha DT125 F and I am turning the bike into a cafe racer. To make it a cleaner look I want to take off the air box and put an air filter on the carbarator. My understanding is that I need to jet my carbs before doing this. How would I jet the carb specifically so I can have just an air filter instead of the air box? Any help on this would be greatly appricated! Cheers! Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted December 3, 2013 Moderator Share Posted December 3, 2013 Trial and error. A foam type filter should let more air into the carb which will make the mixture lean and increase the risk of a seizure. To compensate for this you need to increase the flow of fuel. To do this you increase the size of the jets in the carb and consider allowing more fuel through the needle (midrange). Open the carb and see what jet sizes you have in the main and pilot jets. Buy some bigger ones, it is best if you buy a range but 20 up on the main jet and 2.5 on the pilot would be a good starting point. Also move the needle circlip one notch down the needle (towards the pointy end). Fit the carb back on and attach the filter and start it up. Use a new spark plug. See how it idles and adjust this then see how it rides, taking care and only a very short journey. When riding, and safe to do so, cut the engine using the kill switch and pull in somewhere safe. Take the plug out - bearing in mind it will be hot - and see what the plug looks like for colour. Using the plug colour and how the bike pulls identify if you need to change the jets to a slightly bigger or smaller size. During this you run a higher risk of seizure so slowly does it. The main affects the top end, the needle midrange and the pilot the tickover. That is about it. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted December 3, 2013 Moderator Share Posted December 3, 2013 How will it give a cleaner look. It is there to make the bike run well as they really dont respond well to pods. Been there and tried it. Only work at WOT and that kills Dt's Where will you put everything mounted to it, battery, fuses, oil tank etc. Its hardly chubby to start with. Link to comment Share on other sites More sharing options...
Surfrat25 Posted December 5, 2013 Author Share Posted December 5, 2013 Thank you DirtyDT i changed all the parts accordingly to what you have said, the bike runs great I went up to a size 130 on the main jet and a 27.5 on the pilot jet and it's working great! I will post pics to show the progress! Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted December 5, 2013 Moderator Share Posted December 5, 2013 Glad it is running ok. I do have to agree with cynic and say I am not a lover of pods. They do have their place though. Just keep an eye on the plug colour. The new 2 stroke oils are much better now and this allows a much bigger range of tinkering. Always use a good quality synthetic oil - I prefer castrol power 1 racing 2 stroke. That said, Blackhat gave me some carplan oil at squires and my bike ran fine with that in it. It smells a bit funny (but that could have been me after 2 days camping). Link to comment Share on other sites More sharing options...
blackhat250 Posted December 5, 2013 Share Posted December 5, 2013 Blackhat gave me some carplan oil at squires and my bike ran fine with that in it. It smells a bit funny (but that could have been me after 2 days camping). , you shudda left that sausage, ,, yeh Carlube, £5.99 per litre.. semi -sinth. Big debate on Triple club forum , guys having gummed rings, changing to fully-synth, [silcolene] .. we did France 1800 mls and mate from Edinbrgh rings were stuck, he had fully- snth, [ Halfrauds] i"v had top end off My H2 [carlube ] since home, and perfect, I think its more not running hot enuff gums rings,, Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted December 5, 2013 Moderator Share Posted December 5, 2013 , you shudda left that sausage, ........... Kev ate the sacred squires sausage and they got so depressed that they put the place up for sale! ..... yeh Carlube, £5.99 per litre.. semi -sinth. Big debate on Triple club forum , guys having gummed rings, changing to fully-synth, [silcolene] .. we did France 1800 mls and mate from Edinbrgh rings were stuck, he had fully- snth, [ Halfrauds] i"v had top end off My H2 [carlube ] since home, and perfect, I think its more not running hot enuff gums rings,, Castrol power 1 racing is the way to go John. The bike smelt like old underpants that had been worn for a few days. 1 Link to comment Share on other sites More sharing options...
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