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Discussion Starter · #21 ·
Ok i got a couple DPR9Z plugs. Should i change my pilot to a 42? I see alot of 400ex owners changed it to a 42.. I also see alot of owners running a 155-160 main on stock motors above 3k elevation. I read at lower elevation you should run a bigger main due to being to lean??
Im at about 95ft above.
 

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Discussion Starter · #22 ·
Ok im a dumbass... I was just watching videos on top end rebuilds. Noticed they say at tdc the cam lobes point down.. Well for some reason i thought they were pointing up so thats how i installed them... But how is this thing running with the cam 180 degrees off??
 

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There is no such thing as 180* off on the cam timing - the cam turns 1/2 the speed of the crankshaft and the ignition is fired by the crankshaft. There is a spark every 360* of crankshaft rotation (one at TDC of the compression stroke and one at TDC of the exhaust stroke (referred to as 'wasted spark' ignition) - there is no mixture to burn on the exhaust stroke so the spark is there, but does nothing. The engine is assembled with the cam lobes down to ease assembly - with the lobes up, the valves have to opened slightly as the head cover is installed.

Some videos (especially on YouTube) can be helpful and some are 100% wrong - it's up to the viewer to sort through the garbage - not everyone who makes a video knows what they are doing and doing it wrong does not always mean it was wrong, just more difficult than doing it right.

If the ignition was fired by the camshaft, it still would not be wrong because the ignition unit can only be installed on the cam one way. Now if the engine has more than two cylinders or has an odd degree of firing between the cylinders, the spark and valve timing become critical. One of the hardest motors I ever worked on was a Triumph 860 vertical twin - it used a 270* crankshaft (each piston arrived at TDC of the compression stroke 90* apart) and in addition, the camshafts rotated the opposite direction of the crankshaft due to an elaborate chain from the crankshaft to gear a gear and then a split gear drive of the cams.

As to jetting - the stock setting was changed for altitudes above three thousand feet, the main jet is reduced from a 148 to a 142 - since those sizes are only available from Honda, commonly used jets are 145 for a stock setting and a 140 for over 3000' - the stock pilot jet is a 38 and is not changed for high altitude, but the fuel (pilot) screw is turned in one full turn - I have never used a pilot jet larger than a 40, but have run main jets up to 220 depending on the engine setup, but 150 to 160 on the main jest seems to be the sweet spot for me on my engine. I found the 148 main jet a bit lean when using alcohol blended fuel and a 150 helps when using the lower BTU fuel and with all stock components (intake and exhaust) 150 works well with non-ethanol fuel as well - pilot screw needs to turned out 1/2 turn for alcohol fuel, but remains at the stock setting with non-ethanol fuel. For people who buy chit gas (a penny cheaper than the brand name stations) they may get as much as 15% alcohol - at 15%, the pilot jet has to be increased to a 42, the main jet to a 170 and the slide needle raised 1mm and the fuel screw adjusted to whatever setting produces a satisfactory idle - as little as one turn for some and as much as 4 turn out for others. Then they buy gas out of state and bitch that the engine was running fat until they got home and filled up with the chit gas again. I suggested they take 20 to 30 gal of the chit gas with them, b ut they say the gas is cheaper across the border, so why would they want to carry the chit with them.

I don't know - the debate rages on and I have mine running spot on - I take my gas with me when I ride out of state and i don't screw with my carb constantly - I set it once when it was new and haven't had to adjust it since, but I don't change altitude over 1000 feet and I run the same 91 non-ethanol fuel it was set up with.

Here's what the manual says about high altitude
4736
 

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Discussion Starter · #24 ·
If the cam is installed lobes facing up then the valve timing would be off wouldnt it?
This is how it seems to me: cam installed lobes up valves open instantly just before tdc and just after tdc opposed to if cam was installed lobes down where valves are delayed apon being open.
 

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Discussion Starter · #26 ·
I redid the timing just to satisfy me.. I pulled the plug and its black.. Hows it running rich with stock jetting. Should i remove the washers on the needle?
 

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Discussion Starter · #27 ·
Ok new dpr9z, fresh 93 gas. Stock jetting, stock needle setting, lid removed. Warmed up the motor got to 5th gear then wot for about 10 seconds and it still made the noise, shut it off pushed it to garage and pulled the plug.. Its white, ill try to post a pic.
Im going to cover the hole that was cut out of the lid and put it back on..
What jetting would you recommend?
 

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