416 mod

I am about to put an 87mm. piston in my 400EX to make it a 416. Does this require a different head gasket than stock?? I ask because the new stock head gasket is about 86mm in diameter. That would leave about 1mm. gasket in the combustion chamber. That doesn't sound like a good idea to me. If a different gasket is needed, where do I get one? If anyone has done this mod, let me know what you did.

[knighttime]

When I did this mod i got a new gasket set. I ordered all the stuff from Marcum's atv. I highly suggest you put the xr400 cam in your engined if you are already gonna do the 416 kit. It's foolish not to because you will the the whole freakin' engine already opened up.

[400exdad]

Hey Rockosmith! Knightime, I ride with Rocko and I'm trying to talk him into the XR400 cam too! :D Maybe now h'll go for it!!!

Missed you at HollySprings Rocko and looking forward to LBL!!!

Happy New Year!

[86atc250r]

I've been running the OEM gasket for about a year and a half on mine with no trouble.

You can measure the piston to gasket clearance to be sure, can't remember where the cutoff is - been too long since I did mine...

Originally posted by knighttime
When I did this mod i got a new gasket set. I ordered all the stuff from Marcum's atv. I highly suggest you put the xr400 cam in your engined if you are already gonna do the 416 kit. It's foolish not to because you will the the whole freakin' engine already opened up.

Yup you need a cam too....;)

Just follow the links at the top of the page and give Terry a call at Marcum's atv. He is very helpful. I would guess he's going to tell you to get a new head gasket, it seems when I ordered mine from him, the head gasket was 1 mm bigger than the piston. Then you might as well order the xr400 cam also for an extra $125.

[Dave400ex]

Get the Cam too.

Get the cam, yoy will be glad you did.
Depending on where you order the kit from it will come with new gaskets. If you do the work yourself, there is an o-ring at the base of the cyl sleeve, dont damage it when scraping gaskets, the new top end gasket kit does not include one. It is a cheap part but it sucks to have to wait for a new one to get here.

I’m also doing a 416JE Piston kit with Marcum’s CDI Box. But I purchased a White Bros. Cam part# wb1498 is the XR 400 cam better? What is the best way to check valve to piston clearance? I was thinking about using the clay method. Can I use my old head gasket, or do I have to get another head gasket from Marcum’s? I don’t want to reuse the new gasket after I crush the firing ring when doing my checks.

[NJ300ex]

the best way to check valve clearance is with a feeler gauge.

Originally posted by NJ300ex
the best way to check valve clearance is with a feeler gauge.

I need to check valve to piston clearence. Paper work with cam says I need .050 on intake and .080 for exaust valves. with clay in valve pockets of piston. Paper work also says I need to check valve to valve clearence.

[NJ300ex]

sorry i didn't see it said valve to piston clearance.

You should be able to check the valve to valve clearance by turning over the cam in the assembled head while you watch the valves (like in a vise or clamped to a bench.) To check the valve to piston clearance spray WD-40 on the piston and put a small ball of clay in each valve pocket. Spray the combustion chamber and assemble the top end using your old head gasket. Torque all the bolts, adjust the timing chain and valves. The WD-40 helps the clay to slide alittle and clean off alittle easier. Dissassemble the top end and using a knife or razor blade cut the clay in the valve pockets in two carefully removing 1/2 of it. Using a feeler guage, check the thickness of the clay. If everything is ok clean up the clay and re assemble the engine using a new head gasket. Good luck,Jim.

[416 EXtreme]

when i had to re-rimg my 416 i bought a new head gasket by cometic,it was for the 416.

What kind of H.P. increase could I expect?
Piston, cam, rev limiter,K&N Power Kit .170 main, dropped on thooth on counter sprocket and FMF Power Core4-2, OEM headpipe


Thanks for the school...Jim

[Dave400ex]

How do you like your TC Motor? I want to do his XC Motor Setup. I was going to do a 425, but I think I might do a 416 now. How much of a difference did the 416 Piston and Cam make?

[mysticfalcon]

I am thinking about getting a 416 also. what kind of gain can i expect form the 416 with 10:1 compresion and a cam. I need to be able to run pump gas cause theres nowhere to get gas higher than 92 octane within 2 hours. How much did those of you that have done it spend from start to finish? I gotta save for it so i want to know how long im gonna be saving for.

I can't tell you what kind of performance increase cause I'm still waiting for my cyl. As for the cost, this is what I have invested.

Piston Kit JE 416CC:10.8:1 $140.95
Rev box $104.95
White Bros cam $142.02
Machine shop for sleeve $50.00
Exhaust gasket $3.00

Piston and rev box came from Marcum's ATV. I purchased the cam a local bike shop


This is the quote for head work from Marcum's ATV

To port the head and flow is 65 dollars plus return shipping. The three angle valve job is $75 bucks for the labor. I recommend replacement of the valves when you do this. They are generally 25 to 30 bucks each for the good stuff. Let me know.

Thanks
Terry

[out4sand]

What are the people that have the 416 kit running for a carb? I have ordered the parts needed for the 416 kit- piston (had to go with race gas compression), cam (XR400), & gaskets. While the motor is aprat I will also have it ported. I don't know that I will have the cash for a new carb now so I was wondering how the stock one performed with the motor upgrade or if anyone had any inexpensive ideas until I have the extra cash for a quicksilver carb?

[Dave400ex]

KonBud, Let us know the Power Increase when you get it put together.

Out4Sand, The Stock Carb will work fine. Most of the guys on here with the 416 still run the stock carb. If you want something cheap, Curtis Sparks can mod your stock carb for $175. I wouldn`t spend that kind of money on something you want to replace. I would just save and get the 39mm FCR carb.

[86atc250r]

The JE piston setup @ around 10.8:1 with an XR cam made a very nice improvement in power.

If you want to go the cheap route, remove the choke from your stock carb.

If you want to make some real power, get the FCR. When I installed mine, it was like doing the first mods all over again.

There's a couple group buys on our e-mail list for the FCR - one is $355 and the other is around $375.

Right now, with my setup, I can pull piped Raptors, I have great power everywhere, and get better fuel economy than stock, which is really important for the 2 hour plus races...

[Dave400ex]

Gabe, what all do you have done to your Motor?

[86atc250r]

Lightened JE 87mm (416cc) 10.8:1 piston
XR400 cam
Keihin FCR 39mm carb
Minor port cleanup/matching/bowl work
combustion chamber polishing
Sparks X-4 full exhaust
modified airbox
Sparks HD cam chain
modified upper cam sprocket (adjustable)

[NJ300ex]

Gabe, what did you do first suspension or motor work?

[86atc250r]

Suspension.

The 400 needs suspension work more than engine work in cross country or MX racing.

[Dave400ex]

Yeah I think I will get the Shocks before I do the Motor. I like the Power of my 400 now. For the XC races around here you don`t need a lot of power. A Stock 300EX beat all kinds of Tricked Out Raptors in the one race.

[goochy]

Rocksmith, you better go bigger!!!!!!!!!!!!!!!!!!:blah :blah :blah :blah :macho :macho

[mysticfalcon]

How much work is required to take apart the motor to put in the 416 kit and cam and wht parts need to be sent in? Will i be able to do the work myself or should i send in the whole motor? i am a very mechanical person but i have never done any motor work before when i wanted it to run again :) i disected my old car when it died. would it be worthwhile to have the port and valve job or would that just meke for more stuff to ship? sorry bout the long post but i got a lot to learn and i want to learn all i can.

Hey Goochy!! I think that the 10.8:1 416 with XR400 cam will be more than I need. I am old and can't afford to get hurt!! Don't heal as fast as I used to.

[Dave400ex]

The 416 Piston and Cam will be a lot better than Stock. RockoSmith can always upgrade if he wants more Power.

Seat of the pants power-wise, my 416 hangs right with modded 430EX's, 250r's, Raptors and DS650's on pavement drags (thru top speed), and I walk away from all of them on sand/dirt drags (easily in some cases).

Actual measured HP, I don't know for sure, but my quad shop told me I am in the mid to upper 30's for HP. This appears true based on my performance against these other mid-30HP quads in straight line drags.

Just took my fresh 416 out this weekend, and it has twice the power it seems like over a stock 400ex. It's a night and day difference. I'm talkin 3rd gear wheelies in the snow,,I've still got the stock carb and if Like Gabe said adding a new FCR carb is like doin the motor rebuild all over again,,I couldn't imagine,, the 416 kti is the way to go guys,,hands down.. My only problem is a I got a bent axle so I really couldn't hammer down,,felt like the bike was gonna shake apart.. :(

[MR. HONDA EX'S]

I've rode my cuz's 416 and like Rico says it's a night and day differance. These thing rock, it's my next mod on my 400. He's also got an FCR 39mm carb and that where the power is.

Hey, RICO did you get all of your stuff send out and chromed out on your bike. If you did post some pics.

The most garentied way to check valve clearance is with a feeler gauge.

:confused: :devil :grr

[Dave400ex]

I can`t wait to do the Motor on mine. I have to get the Suspension done first though. I think I will get the 416. I have heard nothing bad about it. Plus this Motor does not cost much to build.

Rico, are you going to get the Free Durablue Axle? I would get the Free Axle and try to sell it for $200 plus and then get a Lonestar or RPM Axle.

[416 EXtreme]

I raced my 416 all last season and had no problems.I was still using the stock carb so there were some power still not used.now i'm in the middle of going up to a 425.I just got my rod and crank back,just waiting for the piston and head to get coated.I opted to go with tc's 38mm lectron.a friend has the fcr,it works great,a little bog down low but overall it makes alot of power,but the lectron is half the price and does the job well.

[86atc250r]

Your buddy's low end bog is a tuning problem - mine and a buddy's with a more aggressive cam doesn't exhibit this, however we did make sure they were tuned in correctly.

Think twice about the Lectron - there are some very good reasons it's half the price and people still buy FCRs and Edelbrocks.

[NJ300ex]

Gabe, what cam do you have?

[86atc250r]

I'm currently running the XR400 cam.

We built another 400 identical to mine with a GT Thunder cam for a close buddy.

I run the XR cam because of the racing I do. It has awesome low & mid with a very respectable top with my setup. But the biggest thing is I get better fuel economy than even a stock bike with this setup, which makes 2 hour races not a problem on a single tank of gas (I don't like oversized tanks).

If this were more of a play riding or dune quad, I'd run the GT Thunder cam in it.

[Dave400ex]

416 EXtreme, what did you have done to your Rod and Crank? Are you doing the TC 425 Kit?

Gabe, what do you think of a TC 416 Piston Kit and XC Cam? TC told me the Stock Carb was good for XC Racing and didn`t need replaced. What do you think?

[out4sand]

Which carb do you guys feel is better the FCR or the Edelbrock? My 400 is being outfitted with an XR400 cam & 416 kit as we speak and I would like to get a carb before spring but am unsure which to get.

http://out4sand.tripod.com

[86atc250r]

TC is likely using a JE piston or similar... What compression is he suggesting? If around 10.8:1 then it's an off the shelf piston that should cost around $135. If higher, like 12:1, the it's a custom piston that should probably run around $175.

Never had any experience with the cam grind he is using.

The stock carb works OK with a 416 setup - I've run both ways. However, I got a big boost across the board after going to the FCR. Oddly enough, I noticed a big boost in bottom end and mid which is opposite to the conventional wisedom of going to a larger bore carb.

Going from my 416 setup & stock carb to the FCR was like doing my other mods all over again.

The FCR is a tad more difficult to tune than the stock carb as well as a little more touchy about temperature and conditions, but it's basically the best carb money can currently buy (that's why it's used on all the modern tech, high output 4 strokes being produced today - YZ250F, YZ426F, KTM520, CRF450R, etc).

The only problem with the FCR offered by Sudco, is it's a streetbike version with little overflow venting. The only problem I've had with this is when jetted rich and pulling wheelies, it will have a tendency to bog. The problem is very minimal if jetted correctly and only shows up when I'm doing low speed wheelies beyond the balance point going uphill. If a person was brave and resourceful, they could likely vent it themselves if this was a problem for them.

[86atc250r]

Originally posted by out4sand
Which carb do you guys feel is better the FCR or the Edelbrock? My 400 is being outfitted with an XR400 cam & 416 kit as we speak and I would like to get a carb before spring but am unsure which to get.


Your setup is similar to mine.

Both carbs develop good power over the stock carb.

I like the FCR, for one because the factories trust it on their best 4 stroke bikes. It's also one of the most desired carb setups for the crotch rocket crowd.

The throttle pull is shorter than stock, the Edelbrock is longer than stock. This allows you not only to reach full throttle more quickly, but more importantly, allows you flexibility in your thumb throttle orientation which can greatly reduce thumb fatigue.

The FCR requires no modifications to the machine, it's a true bolt on. The Edelbrock requires trimming on some of the intake parts and grinding of the throttle housing to get full throttle.

The FCR has loads of adjustability. The Edelbrock's "no jets" system scares me. The theory sounds good that you don't have to change jets, but it doesn't appear that there are very many options for fine tuning.

Throttle acutation is very smooth on the FCR due to it's roller mounted slide.

Right now there is a "Group buy" on our 400EX e-mail list for FCR's @ $355. There is another "Group buy" going on for $375 for the FCR on our group thru another individual, so a person can talk to both and order from whoever they think will offer the best customer service. I don't make a dime from any of this - so don't consider my opinion biased.

[out4sand]

thanks 86atc250r, that makes a lot of sense and I totally agree with you on the fine tuning. No jets was one of my major concerns, like you said it sounds great but I personally just am unsure about it. I upgraded the carbs on my banshee to Keihins and have been super happy with the results so I think I will set the 400 up with the FCR.

[416 EXtreme]

i'm getiing a heavy duty rod(carillo) and the crank welded and trued.
86atc.I hear you about the carbs,but i know several people who use the lectron 36 and 38's,the only problem i know of is you have to angle it at about one oclock when you install it.As for the FCR it definitely took some tuning they had to change the pilot and main,they even tried to disconnect the excellerator pump.He has it tuned good now with the pump.I guess the carb is used to a twist throttle rather than thumb.(quick movement)

[Dave400ex]

The TC 425 Piston is $120. I don`t think the 416 would be any more than that. I don`t know what Compression the Piston is.

I think I will get his 416 Piston and Cam.

[rhandw69]

Out4Sand:

Have you seen anyone down in the dunes with the 416 and FCR set up along with the XR cam? Im 3/4 way there, i have the 416 and cam, but Im hesitant on the carb. I guess i really want to be sure its going to the rite thing to do. I mainly am trying to get my bike set up for the sand, so if the carb is the final thing to do then maybe ill do it,,,im just hating to spend the money. I too have heard that you may lose bottom end. That worries me. I realize that most people say that its all about wheel spin for the sand, but to me you really need that bottom end torque to get that jump out of some sand drags, or even some "Idiot Holes".
I could be wrong, maybe you could give a little imput on what you think.
Dune season is rite around the corner!!

[86atc250r]

You will gain bottom with the FCR if you set it up correctly - this goes against the conventional wisedom that people without experience with this swap will tell you, but I've tested my 416/xr cam combo both ways and there is a serious improvement across the board with the FCR, especially in the bottom and mid - this is a NECESSARY mod for the sand.

To give you an idea, I run 16/38 gearing in the tight woods I race, to tame it down & spread the gears out - The bottom end still pulls stumps even with this gearing & 20" 6 ply RAZRs on ring reinforced Douglas .190s (not a light combo).

What are you worried about anyhow, the 416/xr cam setup has tons of bottom anyways.

As I've mentioned before, if you want a carb, now's the time to buy - you won't find a better deal on a new carb than what's being offered on the e-mail list currently.

416 Extreme -
Getting the FCR correct is just a matter of setting the accelerator pump properly and getting it jetted in... I run a 52 pilot and a 168 main in my combo and the quad runs flawlessly. I also played with the pump a bit to get it nailed down to perfection when you hammer it off the bottom (I run a thumb throttle as well).

The 1 o'clock mounting position on the Lectron poses many problems, the lack of an accelerator pump poses some problems (Just ask the XR400 guys what they think about their throttle response & how their bikes start) - do yourself a favor and get a carb that mounts correctly. The lectron is a decent 2 stroke carb, but is very marginal for a 400ex.

I don't have anything to gain from any of this - I just hate to see someone spend $200 on a carb that will make more power on top, but suffer everywhere else compared to stock when you can save up a little more cash and do it right. If you are dead set on the Lectron design, then get the Edelbrock - it's a Lectron that's been "Fixed".

Like I've said before, ever wonder why you've never seen anyone with a YZ426 yank their FCR off and replace it with a Lectron?

There are also at least a few Lectron owners on this board & others that will warn you about not getting one.

[416 EXtreme]

gabe,with the gearing you run do you still have a case saver?

[out4sand]

rhandw69 - I sure haven't seen anyone with the FCR carb yet. For that matter I have yet to see anyone running the quicksilver in person either. I do like what the others have said about the FCR in the forums though and I am not so sure that I am sold on the jettless carb. There is a good possibility that I may have one before summer rolls around though. I took my 400 down last night to the shop and had my buddy tear off the top end to get it ready for the 416 kit & cam. It should be all back together by early next week. Depending on how my pocket books looks after it's all done and said I may go ahead and order the carb. If I do I will let you know how it works out.

http://out4sand.tripod.com

[NJ300ex]

out4sand- you just said you had a pocket book. J/K