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1/2 of Gordon's?

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So I finally got to spend some quality time in the garage this evening and finish the projects I started last weekend including the Gordon Mods. However since none of my drill bits are even close to being sharp I didn't get to drilling out the muffler ala Gordon style. So I bolted it back up and did a test ride with the new jetting, Uni Filter, no Snorkel, stock header welds.

:banghead: Oh man is that a different bike! The PO rode the thing for 8 years with the stock jetting. The bog was so bad I don't know how he ever did any technical trail riding. Now the bog is there but much less significant. It also started on the 2nd kick and wheelies with no clutch in 3rd gear (stock gearing) when before it would only come up if I clutched in 2nd. IMO the bike is much improved.

Should I bother going after the header welds and exhaust? :) I'm not looking for more top end but some low end would be good if available.

Other Recent Mods:

-New Bars

-New Grips

-BRP Triple Clamp

-Scotts Damper (stole from the 250L)

-Braking Front Rotor

-Moose Tool Bag

-Solid Choke Plate

In a box waiting:

-13T CS Sprocket

-Drill and Tap for steering stops

-LED Rear Turn Signals

-Trail Tech Endurance (Steeling from 250L)

-GPS Mount (Steeling from 250L)

-Remount Bark Busters

-New Side Covers

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I guess you're having to extend the steering stops for the Scotts Damper?

I would go ahead and at least drill the muffler. I started with 3 holes, am now running 4. You can always plug them with 1/4x20 setscrews later if you want/need to.

Got a grinder, you can resharpen your drill bits easily enough yourself. If you do drill, center-punch your hole first.

What jetting have you ended up with so far? Elevation?

Just spend some more time fine tuning the jetting/fuel screw and you'll be a happy camper.

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Won't opening up the exhaust flow (header welds, drilling the muffler) reduce the bottom end and move the powerband up the RPM range slightly?

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Not noticably, not like you're fearing. If you ran without spark arrestor/baffle installed, then yes. Alot of people say that this mod doesn't do near as much as a complete new free flowing muffler for power, like a Big Gun or some other, and that's true, but with those you will lose some bottom end because they're made for increased mid to top end.

The stock muffler is a good can, the idea behind the Gordon mod to it is to make it a little freer flowing, tunable in essence(using the 1/4x20 setscrews if needed) to make what you do to the entire system by yanking the snorkle, installing the UNI and rejetting, work better. If you provide more air flow in and jet accordingly for that notion, you have to provide more flow out or you start creating a bottleneck situation. True, it's the bottleneck situation that provides low end torque, and the engineers figured the desired/optimal amount/flow, for the regulations they had to abide by, in the original design of the entire system. But when you alter the original specs of intake flow thru the airbox, thru the carb(increasing venturi effect and providing more air for the current jetting, altering the fuel/air ratio), you need to derestrict flow thru the exhaust somewhat also to keep the balance the original design had.

If you derestricted the exhaust and did nothing to increase intake, then you'd lose low end torque.

Hope I described that well enough.

Some people don't even mess with the header welds, don't need to. Some welds are much worse than others. Don't do all the exhaust mods at once. Drill the arrestor, jet, tune and ride it. See what you think. Only then decide if you want to try clean up the header welds.

Won't opening up the exhaust flow (header welds, drilling the muffler) reduce the bottom end and move the powerband up the RPM range slightly?

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I cored out the entire baffle while leaving the spark arrestor and it sounds great. It is not overly loud either. much quieter than my aftermarket pipe. I am actually in the process of getting a new tip and quiet core for my exhaust pipe.

THis what i did to the stock pipe.

http://www.thumpertalk.com/forum/showthread.php?t=725019&highlight=exhaust+tips

I would do the header welds as well.

IMO you are not going to lose a noticeable about amount of low end with these mods on a xr400. the stroke on this bike is huge compared to newer bikes. it makes great low end because of physical girth not specifically tuned air flow.

Good luck and welcome to the club!

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Redrider you must be falling in love with the 400L, if your stealing parts from your beloved XR280L.

Why not show us a few pictures, i know i have day dreamed about a 400L.

Glad your enjoying the new bike!

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So I finally got to spend some quality time in the garage this evening and finish the projects I started last weekend including the Gordon Mods. However since none of my drill bits are even close to being sharp I didn't get to drilling out the muffler ala Gordon style. So I bolted it back up and did a test ride with the new jetting, Uni Filter, no Snorkel, stock header welds.

:banghead: Oh man is that a different bike! The PO rode the thing for 8 years with the stock jetting. The bog was so bad I don't know how he ever did any technical trail riding. Now the bog is there but much less significant. It also started on the 2nd kick and wheelies with no clutch in 3rd gear (stock gearing) when before it would only come up if I clutched in 2nd. IMO the bike is much improved.

Should I bother going after the header welds and exhaust? :) I'm not looking for more top end but some low end would be good if available.

Other Recent Mods:

-New Bars

-New Grips

-BRP Triple Clamp

-Scotts Damper (stole from the 250L)

-Braking Front Rotor

-Moose Tool Bag

-Solid Choke Plate

In a box waiting:

-13T CS Sprocket

-Drill and Tap for steering stops

-LED Rear Turn Signals

-Trail Tech Endurance (Steeling from 250L)

-GPS Mount (Steeling from 250L)

-Remount Bark Busters

-New Side Covers

what jets did you put in it?

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Thanks for all of the replies everyone. :) I’ve been in the garage the whole weekend so I didn’t get back on TT.

I guess you're having to extend the steering stops for the Scotts Damper?

What jetting have you ended up with so far? Elevation?

Just spend some more time fine tuning the jetting/fuel screw and you'll be a happy camper.

what jets did you put in it?

I started with 58/158 since I ride from 0’ to 5500’. I think it’s running a bit rich right now with the exhaust still plugged at both ends. But I think once it is warmer and with the range in altitude I ride I think it should be a good place to start.

I haven’t touched the mixture screw yet, I’m going to leave that to a warmer day when I can do a plug check and test it as some altitude.

I did extend the steering stops with a 8/32 SS cap screw for the damper. Would have gone metric but the local hardware store doesn't have metric taps. :banghead: On the forward mount with BRP triple clamp the damper arm hits the bar clamp…You think they would have planned for that one. The 400 w/ the steering stops still turns as tight as my 280L w/o steering stops so I think it should be fine.

I cored out the entire baffle while leaving the spark arrestor and it sounds great. It is not overly loud either. much quieter than my aftermarket pipe. I am actually in the process of getting a new tip and quiet core for my exhaust pipe. THis what i did to the stock pipe. http://www.thumpertalk.com/forum/showthread.php?t=725019&highlight=exhaust+tips I would do the header welds as well. IMO you are not going to lose a noticeable about amount of low end with these mods on a xr400. the stroke on this bike is huge compared to newer bikes. it makes great low end because of physical girth not specifically tuned air flow. Good luck and welcome to the club!

I plan to eventually do the Gordon style drill first, then if that doesn’t suit me I’m going the 2” hole saw route. Thanks for the link!

Redrider you must be falling in love with the 400L, if your stealing parts from your beloved XR280L. Why not show us a few pictures, i know i have day dreamed about a 400L. Glad your enjoying the new bike!

I do really like the 400, it has everything that the 250 has but more… More power, more parts available, more weight :banghead: However I’m not selling the 280L until I’m 100% the 400 is the better bike for what I do. That being said I have stole a few parts of the 280L and I’ve already spent a bit of money on the 400!

Pictures will come… I took some this weekend of the mods to document what I did. I don’t know how many times I’ve referred to the pictures of my 280L when I had the oil cooler in its early stages or when I did the 280 kit.

I took a few of the bars and routing because I went with Tall ATV bars and the Scotts forward mount and routing seems to be an issue with the setup.

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Well if you do end up selling your 280, wanna switch out side covers? hahaha

ill give ya all you have into that oil cooler and more to get that setup.

just something to think about.

have fun redrider!

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Well if you do end up selling your 280, wanna switch out side covers? hahaha

ill give ya all you have into that oil cooler and more to get that setup.

just something to think about.

have fun redrider!

If I do sell the 280 then I will first try to sell it complete as is for simplistic sake. If it doesn't sell I may start parting out the aftermarket goodies separately and selling the bike in a more stock form (stock light, stock tank, stock bars, stock speedo, stock springs. The oil cooler is reversible but kind of a PITA to remove so I'm not sure if I would remove that. However, let me know if you would like to come see it want me to take any specific pictures of the setup before I sell.

Actually I do have a spare 250R side cover that I didn't use because of a crack in it. I'm too OCD to JB weld it but since it isn't a through crack then I think it would be usable. PM me if interested.

http://www.thumpertalk.com/forum/showpost.php?p=6349654&postcount=19

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Why not show us a few pictures, i know i have day dreamed about a 400L.

Glad your enjoying the new bike!

Got some pictures up the garage. Enjoy!

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