starting some engine work

Discussion in 'General Questions' started by Ryusei139, Sep 18, 2014.

  1. Ryusei139

    Ryusei139 New Member

    I just pulled off the head after 1200 miles. Should I be worried, it looks like somethings wrong. I'm about to raise my exhaust 2 mm and clean up any casting in the cylinder.

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  2. patthesoundguy

    patthesoundguy New Member

    That is just carbon build up and is perfectly normal in a two stroke motor. Get your self some carb cleaner and some steel wool and scrub it down. I'd pull your piston and clean it as well. When you do your porting make sure to match the intake to the way intake port on the cylinde, they never match. And Rough up the intake with a stone on the dremel or die grinder to give a cats tougne finish. Just port matching the intake makes a huge difference. A modded ehaust with a raised ex port and portmatched intake will be a whole new bike
    Ryusei139 likes this.
  3. HeadSmess

    HeadSmess Well-Known Member

    ive never really bothered with raising the exhaust. always felt better widening them.

    though some raising is necessary to develop the required radius...DONT grind the top (or bottom) of the port square! make it oval shape, far gentler on the rings.

    its an idea to get both transfer ports cleaned (theres always a lot of casting flash left in there) and MATCHED, so they open at exactly the same time. requires some delicate handling to get a good result. also an idea to round the tops of a bit too.getting in there with standard tools is a nightmare...i got dentist drills specifically for doing such things... but a 6mm(or 1/4") endmill will fit in a die grinder and will "just" clean up the flash.

    chamfer the edges of the ports slightly. once again...gentler on the rings.

    also, match the transfers to the crankcase, theres a good 3mm overlap in most engines down there. overlap is bad news :)
  4. patthesoundguy

    patthesoundguy New Member

    What great advice. I left my exhaust port at the stock timing and widened it as you mentioned. I did that for two reasons, i wanted to see how the portmatching changed the performance and i diddnt want to go too far in rasing the ex port and have performance suffer. I am very happy with the motor with the stock ex. port timing. Sometimes stuff is best left alone if it works well. 2mm might be way too much in that motor any way. Id go a little at a time. Raise the port little then try it if you are going to raise it. Try 1mm first.
  5. Fabian

    Fabian Well-Known Member

    Oh shush now HeadSmess. Stop giving away the most important modification, because i will loose my technical advantage to those people raising their exhaust ports and consequently destroying their low and midrange torque band; making the bike a total pig to ride.

    I wish you would keep quiet on this issue, so i can keep my low rpm power advantage over those people who rev the rings out of their engine and in most cases, go slower (than a stock standard engine) after their cylinder porting modifications.
  6. Ryusei139

    Ryusei139 New Member

    Thank for the advice guys I'm getting a sturmey archer xl-rd5. Then I'm going to match the intake and exhaust (widen the exhaust and raise 1 mm) and match the transfers. I just raised the compression by shaving the head on glass and sand paper. Talk about a sore arm lol.