Author Topic: Porting Advice Needed (Read 9817 times)

mrmoto · « **on:** July 08, 2013, 01:43:50 PM »

When I recently did the complete rebuild of my ATC motor I had CT Racing (Allen Knowles) do some porting. I gave them the specs for the rest of the build and what I desired, and my cylinder, piston, and head. That was over a year ago before I found the 250R communities and was ignorant. I was told the cylinder now has basic MX porting and was decked very little.

Now I am not sure it is ported for optimal performance as I have learned generally speaking MX porting is not optimal for a top end motor. I just didn't know enough to be more exact in my porting desire and request. Nor do I have enough experience to look inside a cylinder and know what type of porting it has. It may be optimal

So now I am considering pulling the cylinder back off and sending it somewhere else to get a second opinion and more porting if needed. Or should I not bother considering the motor is pretty close to stock? Here are my specs

Type of riding - Southern California dunes and desert
'85 ATC
Original OEM cylinder
Bore - 66.5
Stroke - Stock
Piston - Pro-X cast piston
Compression - 190 psi
Head - Stock
Pipe - PT Hi Rev Fatboy 2 silencer
Reeds - v-Force 3
Carb - 38 AS
Ignition - '01 CR250
Fuel - 100 oct Unocal 76 pump

Thanks!

motofool250r · « **Reply #1 on:** July 08, 2013, 03:10:51 PM »

whats your budget? and or goal just more power ina duner style motor?

mrmoto · « **Reply #2 on:** July 08, 2013, 03:42:35 PM »

Yes my goal more power in a duner style motor. That being said I would like this motor to be tuned optimally with reliability intact as much as possible. Best it can be tuned for what it is. I wanna keep it a pretty close to a stock looking ATC. I am the original owner and I want to keep it looking close to what it was when I bought it new in '85. When I build a rocket it will be a whole new machine.

I am hoping not to go over 500.00. Fine tuning the porting on this particular motor may not produce much gain that can be felt in the seat of the pants but at least I will be happy knowing it was done right, which it may already be!! If someone looks at it and says "you just need a little bit here and there, 200.00" that would be fantastic but I don't expect that.

motofool250r · « **Reply #3 on:** July 08, 2013, 03:55:40 PM »

most people i would consider at the top of the porting world are gonna want around 350-450$ to port a cylinder.
generally you do a new bore at the same time, so thats 200$ in itself (50$ bore 150$ piston kit)

to keep the oem cylinder and get the most power possible, +4mm crank(+6 if money no object) and port job, but your looking at 250$ plus port work and gaskets/piston kit

mrmoto · « **Reply #4 on:** July 08, 2013, 04:49:29 PM »

Is boring it a must do? The whole motor only has 6 break-in heat cycles and 20 minutes of riding on it. Who would you recommend I have look at it?

I have read some negative things about CT in the past, but that was on the "other" site so I take that with a grain of salt. I would however like new eyes and an opinion on it

udontknowme · « **Reply #5 on:** July 08, 2013, 07:30:39 PM »

sounds pretty fresh. assuming the clearance is good, theres no need to touch the bore. figure out the port timing with a degree wheel then post some photos to get a idea of the widths and stuff like that then im sure somebody can tell you if your better off leaving it alone or if theres some changes you could do.

mrmoto · « **Reply #6 on:** July 08, 2013, 07:58:23 PM »

Ok sounds good. I have seen the "How to" for port timing in the Tech forum. I will order a wheel tonight. Thanks guys!

motofool250r · « **Reply #7 on:** July 08, 2013, 08:21:23 PM »

the reason you bore it as its likely the porting tool would get off track and touch the cylinder wall at some point the bore cleans it up smooth again

rsss396 · « **Reply #8 on:** July 08, 2013, 08:51:32 PM »

you can still run a cylinder bore with some pecker tracks but most porters don't like to send out their work looking like that, because thats all the customer will focus on not realizing how hard it really is to port a cylinder with out a slip up.

mrmoto · « **Reply #9 on:** July 08, 2013, 10:04:44 PM »

That''s completely understandable. I ordered the timing wheel. When that arrives I will go from the there. One bridge at a time...

rsss396 · « **Reply #10 on:** July 08, 2013, 10:22:45 PM »

if you just widen the exhaust port you really can do this without knowing much at all, you just need some 6" long carbide burrs and a air die grinder.

you can mess things up when raising the exhaust if you do not have it mapped out.

keep us up to date and we can walk you thru a simple port job that can be done by most at home, nothing crazy but a improvement.

mrmoto · « **Reply #11 on:** July 08, 2013, 11:45:29 PM »

Will do

udontknowme · « **Reply #12 on:** July 09, 2013, 12:29:07 AM »

IMO before you go droppin a bunch of cash on tools maybe post some pics of what you got or email em to rsss396. im sure allen left alot to be desired but just to be on the safe side have someone here check what you got first. then you can get a better idea of exactly what tools you need to do the job. alot of online places have carbide cutters but your probly looking at atleast a week to get em. if your in a hurry and have a local fastenal they can usually get em in 2 or 3 days but i think theyre a few bucks more

mrmoto · « **Reply #13 on:** July 09, 2013, 12:51:03 AM »

No I am in no hurry. I bought a straight/inline die grinder off ebay for best offer but I had been looking at those for months now. So I would just need burrs now.

I am going to wait until I get the port timing and some good pics on here for you guys to see before I do anything else.

And just FYI it now runs pretty good now and I believe it to still be pretty rich. It has a small bog in the middle that I think a DGH needle will cure.

udontknowme · « **Reply #14 on:** July 09, 2013, 01:32:01 AM »

alot of free stuff on macdizzy that will help if you got time to read some of it http://www.macdizzy.com/