To Port & Polish or To Big Bore for the 400ex

[zuLi0]

I've been talking to a few people and reading up on the forums. Alot of people on the forums are real happy with there big bore, but the guys around here say that with a port and polish job, and some other misc. motor work that they are 440 eaters. What do you think would be better to do. 440 sounds meaner but if the port and polish job is gonna rock I'd like to just go that route.

Well a port/polish really shines with a bigger breathing carb,,,doin it with a stock carb is peein in the wind. Get a high comp piston and more aggressive cam and then you'll be out running with the big dogs. A port and polish is NOT gonna give more power over a big bore kit,,,,again unless you add a bigger carb.

[Blackguywithouta400]

You cant beat it, go with the bore, you get more HP and you will love it, your not going to get power enought to do 5th gear wheelies from a port and polish.

[MOFO]

do both...big bore with a port and polish (& bigger carb)...then you will have the best of both worlds.



Eric

[ChadEXer]

I have heard quite a few people say it doesnt make a diiference porting unless you have a bigger carb. Well when I ordered my 416 from Terry Marcum he said that is BS and I definately should port it. So I had the 416 kit installed at first and didnt port it. i rode it around a couple of days to get used to the new found power. Then I had my best friend pull the head back apart and took it to the machine shop and had the full race port done along with borring a little on the inside of my Yoshimura headpipes. All I can say is it made a helluva lotta difference to me!! It made my 400 sound different too. Its sounds awesome. But that is with the 416 and stock carb. I would have no idea how much of a difference just porting would make. My good friend also has a 416 kit with 11.1 compression and mine is 10.8:1 and his has no porting and we ran them against each other just yesterday. let me just say he is getting his ported and polished Friday. He has been riding SPORT ATV's for years and I just got into SPORT ATVing the end of last year so he probably knows how to ride a little better than me. Then again,,,maybe not!

[VegasEx'r]

I ordered a 416 piston & cam yesterday from Marcum's & he told me that a port/polish job would make a huge difference, too. I was kinda suprised that he said to keep the stock carb instead of getting an FCR carb, but he really recommended a port & polish to the head.

[ChadEXer]

Yeap. Thats the same thing he said to me and he was right. He said the 400 is definately not under carbed and you really shouldnt even get an aftermarket carb unless you really go big on the motor!!
Hey VegasExr. Let me know how that 16t front sprocket works. I have been thinkin about puttin one on my 416 but im not sure. Im going to the drag races this weekend and Terry said I should keep the stocker. What size tires you running?? Also a couple of tips for you. You will prolly have to go to a 170 main jet with the 416. I did. Also. I think Big Gun pipes are nice and sound good but I had the full system Big Gun pipe on before I got the 416 and traded it for the Yoshimura and it made a huge difference. The headpipes are just way too small on the Big Gun. Are you running stock gearing now? If you can run the 15t front with the 416 before you switch to the 16t and tell me what kind of difference it makes.
Thanks

I've heard both,,but I was waiting for someone to get the 416 kit get used to the power then have a port/polish done with the stock carb and see if they notice a difference. It's great how every engine builder has different views and opinions regarding how engine's act...I guess if it really makes that much difference,,I'm gonna have to send my head off to terry and have the mild port work done.

[ChadEXer]

I had the guy at thee machine shop cut into mine real good. I told him to port it as much as you can withaout starting to sacrifice reliability. Thats what he did. He is very good. He matched the porting together coming from the carb. He said that if you leave it with a "lip" it wont be as good. He knows what hes doing.
Hey Rico. What kind of difference did it make when you had your flywheel lightened. Im still thinking about having mine done.
Thanks

[Mity Mo]

I am a full blown believer in porting the head. I have a big bore with the FCR carb and port &polish work. A guy I raced against only had the big bore and carb, I ate him alive. Port work doesnt matter if its stock or full race carbs, any engine can benefit from portwork. But a larger carb will increase the performance 3 fold. Mo:p

[VegasEx'r]

I'll let you know how the 16t sprocket does. Terry said it would fit w/ the stock case saver, but it looks really tight. I am running the stock tires (still) on the trails & 20" Sand Skates at the dunes, and I think that the 16t may be the way to go for the trails, and the stock gearing might be best for the dunes. I've heard many people say the same thing about the yoshi exhaust, so I am thinking about it, but that will be a while off. The other thing Terry told me to do was pull out the choke & shave off the 2 "fins" that are behind it (but don't shave the accelerator pump). two questions for you: Are you using a 42 pilot jet, or something bigger? Did you switch to a different spark plug with your current setup, or did you leave it stock?

[JhallettEX]

Man, you guys have me thinkin and a little pissed off now. I just bought a FCR 39mm carb, And now it sounds like I should have just saved money and gotten a port and polish job. I might be able to back out of this carb deal still. What should I do? And by the way I am getting the carb for only $300/Delivered. Whats up?

[Dave400ex]

For $300 I would still get the Carb. It will add Power. Then get a Port and Polish some day.

[ChadEXer]

I read on here about removing the choke and I asked my mechanic and he said it definately helps so I had him do it when he first done the kit. So I had it and the 416 done at the same time so I dont really know HOW much it helped but I have heard from many that it does so I had mine done. As for the pilot jet im not sure. my mechanic done the work and all he told me was he put a 170 main in it. I heard from my mechanic and Duncan Racing that a colder plug helps lower the head temp by 5 degrees so Im running a DP9EA instead of the DP8EA(stock). Im lucky that my good friend is a mechanic and has been working on quads for years. He hooks me up and he knows what hes doing. He has one of the fastest 250R's in the country. I will ask him what pilot jet he put in it today and I will let you know here. I gotta take it back to him to get the valves adjusted. Also I know another guy who has a 16t front sprocket and if im not mistaken it seems like he said he had to shave a bit off the stock case saver to fit the sprocket. He sold his 400 a little while ago. It was stock and it pulled the 16t fine he said. But Terry told me to stay with the stock so I will just wait and see what you think about it when you get your on.
Thanks

[R-Crazy]

how much does porting and polishing cost?

dave

[Mity Mo]

Rates in my area (st Louis) range from mild at $175 to wild $250. I would think that is a pretty fair price. You dont want to goto a guy who doesnt have a clue on how to do it for Quads. guys who work on bikes (2-wheelers) sometimes port for different timing than on a quad. So be sure to use a good mechanic that works on quads. And if they had a flow meter that would even be better. Mo

[ChadEXer]

I live in TX and had my wild port and polish and porting of the Yoshi headpipes and the sleeve from the carb done for $100. This is by a guy who has been doing it for years and he done a awesome job.