Author Topic: Who can bore my 39 pwk to 40.5? (Read 5624 times)

Dirt man · « **on:** August 10, 2014, 11:38:00 PM »

I'm running a led/esr 363 and I have a spare 39mm pwk. I was looking for someone to bore the carb to 40.5. Also I run a mid port will this be a dumb move for me? This is a dune only more that I run wot most of the time! All or nothing

2ndmoto · « **Reply #1 on:** August 11, 2014, 01:25:06 AM »

LED can bore it for you. Good move? Its all up to the riding style. I run 38mm on my big bores because I like to short shift them. If you are WOF, it might be a good switch for you.

Best regards
-Jason

pinned250r · « **Reply #2 on:** August 11, 2014, 09:13:47 AM »

Wait, so you've been that fast with a 39 this whole time!?!? Or do you have a 40.5 in it and just want a spare?

Ps all, I don't think there is a single person faster than this guy.... I use to think I was fast.

patman13mia · « **Reply #3 on:** August 11, 2014, 03:41:36 PM »

dang i have that exact same question. so would the bigger carb take a noticeable amount from the bottom end?

Jerry Hall · « **Reply #4 on:** August 11, 2014, 08:26:36 PM »

Quote from: patman13mia;40754

dang i have that exact same question. so would the bigger carb take a noticeable amount from the bottom end?

The big carb will hurt the power below about 4500 RPM. The power will be about the same from 4500 to 6000 RPM. The big carb will usually show a gain above 6500 RPM if your porting and pipe like each other or your engine is modified enough for it to make around 43 hp or more to the rear wheels.

The majority of the good pipes need the RPM to be kept above 6000 RPM to keep the engine "on the pipe".

I define low end to "mean" the beginning of the USABLE POWER CURVE. On the 250R engine, I define the low end of the usable power curve occurs from about 5500 RPM to 6500. Mid range from 6500 to about 7500 RPM and top end from about 7500 to 9000 RPM

Dirt man · « **Reply #5 on:** August 11, 2014, 10:04:22 PM »

It's hard to know what my rpm is when I'm lugging up a dune or can't downshift cause hanging on is all I can do at the moment. Sounds like it would be worth a shot. No Collin I've only ran a 39 with this motor. Flannery always said a 39 was sufficient.

Jerry Hall · « **Reply #6 on:** August 12, 2014, 10:26:37 AM »

Quote from: Dirt man;40764

It's hard to know what my rpm is when I'm lugging up a dune or can't downshift cause hanging on is all I can do at the moment. Sounds like it would be worth a shot. No Collin I've only ran a 39 with this motor. Flannery always said a 39 was sufficient.

If you cannot down shift because it would over-rev the engine, you are turning a lot more than 6500. It is not going to make much difference what size carb you are running if you are needing power when you open the throttle wide open when the engine is running 5500 to 6500 RPM. If you have lugged it down to 5500 to 6000 RPM going up a dune you need to down shift.

toydoc · « **Reply #7 on:** August 13, 2014, 04:03:43 AM »

So Doug did the porting and said the 39 was fine. Doug can bore it and take your $$, but didn't. That says something, I think anyway

udontknowme · « **Reply #8 on:** August 13, 2014, 09:50:24 PM »

ktm been doing something interesting on their new stuff. 250 and 300 use 36pwk a/s. 125 has 38pwk a/s. im sure you gain hp with bigger carb but the lowend signal probly drops off alittle. i prefer bigger carbs like the 41 or 42 or whatever it is from sudco

Dirt man · « **Reply #9 on:** August 23, 2014, 06:29:26 PM »

Quote from: toydoc;40806

So Doug did the porting and said the 39 was fine. Doug can bore it and take your $$, but didn't. That says something, I think anyway

Doug didn't port this cylinder Arlan did. I was at Flannery Motorsports (doug) for a quick hone job and was chatting about bigger carbs and he said not to waste my time and leave it at 39. I do think he is busy and may not be entirely familiar with my type of riding/duning. Also he doesn't like to spend his customers money foolishly.

Dirt man · « **Reply #10 on:** August 23, 2014, 06:30:16 PM »

Quote from: toydoc;40806

So Doug did the porting and said the 39 was fine. Doug can bore it and take your $$, but didn't. That says something, I think anyway

Doug didn't port this cylinder Arlan did. I was at Flannery Motorsports (doug) for a quick hone job and was chatting about bigger carbs and he said not to waste my time and leave it at 39. I do think he is busy and may not be entirely familiar with my type of riding/duning. Also he doesn't like to spend his customers money foolishly.

Dirt man · « **Reply #11 on:** August 23, 2014, 06:39:09 PM »

Jerry hall thanks for your input, you really spelled it out. I would say I'll be trying the bigger carb since I spend most time above 6000 rpm but first I think I should get a bigger air filter set up from the esr eliminater kit I'm currently running.

Jerry Hall · « **Reply #12 on:** August 24, 2014, 06:48:28 PM »

Quote from: Dirt man;41638

Jerry hall thanks for your input, you really spelled it out. I would say I'll be trying the bigger carb since I spend most time above 6000 rpm but first I think I should get a bigger air filter set up from the esr eliminater kit I'm currently running.

Always use an air filter with as much surface area as space on the bike will allow. Increasing the surface area of the filter decreases the restriction and allows slightly more filter oil to be used to improve filtering without increasing restriction.

On TRX Hondas making 50 hp or more I will usually see about 1 to 1.5 hp gain when I remove the 3.5" diameter x 6" long imitation K&N from the air box eliminator kit and install a RU 1840 K&N. The RU 1840 is about 9" long and about 4.5" in diameter. The RU 1840 has 1.5 to 2 times as much surface area as the 3.5" x 6" filter. If you use any of the long filters you should support the end of the filter to prevent the weight of the air filter from pulling the carb out of the reed boot.

Jerry Hall · « **Reply #13 on:** August 24, 2014, 07:13:53 PM »

Quote from: Dirt man;41638

Jerry hall thanks for your input, you really spelled it out. I would say I'll be trying the bigger carb since I spend most time above 6000 rpm but first I think I should get a bigger air filter set up from the esr eliminater kit I'm currently running.

Always use an air filter with as much surface area as space on the bike will allow. Increasing the surface area of the filter decreases the restriction and allows slightly more filter oil to be used to improve filtering without increasing restriction.

On TRX Hondas making 50 hp or more I will usually see about 1 to 1.5 hp gain when I remove the 3.5" diameter x 6" long imitation K&N from the air box eliminator kit and install a RU 1840 K&N. The RU 1840 is about 9" long and about 4.5" in diameter. The RU 1840 has 1.5 to 2 times more surface area than the 3.5" x 6" filter. If you use any of these long filters you should support the end of the filter to prevent the weight of the air filter from pulling the carb out of the reed boot.