116 replies to this topic

[Vegasdirtrider]

I would suggest replacing your stock carb with a 36mm Mikuni, this will solve all your carb problems and will increase your overall performance, good luck.

[Kev_XR Get Help Now]

arcangel said:

Hi I need some help with my 400, it's a 00 xr400r got it second hand, ims 18 ltr tank 15/43 sprockets, snorkel is removed, twin air filter, pilot jet is 52, main 158, i've just repaced the piston with a wiseco 11.1 comp 87mm dia,I cleaned the head, ports and valve reseated the valves,the cam shaft i suspect is standard(can't find any marking on but it appears the auto decomp cam is removed)the welds on the header exhaust looks like it has been ground, the exhaust baffle has been removed with the spark arrester(if you unbolt the three bolt holding the stainless steel end piece there is nothing behind it) I ride at 1000m(3200ft ?) alt, temp ranges 35' c , my location is East Africa.  Now my problem is when riding a a constent speed every few moment the bike give a bit of a cough/hicup)  I can feel the bike drop in rev's and them pic up again, i suspect it is the carb(i've cleaned the carb mackin sure all holes are clean and not blocked, it ideals ok )would i have to change the jets and if so where to 60/160 any help please

Crud in the carb or fuel line or float height.
I am about to deal with the same issue with my XR200R.  The motor surges, up a bit, then down.  I suspect crud in either the carb or the fuel line.  There is a screen on the petcock on this older XR, so I will remove it and see if that is blocked up.   Next, I will set the float height.   The problem could be using up all of the fuel in the carb, starving out, then going again when the float is refueled.   A gummed up float valve could be causing the same issues.

[skinner75 TT Newbie]

kisukun said:

Hello to all from XR LAND! (Japan),
This summer I bought my first Off-road bike an 1996 XR 250 Baja model.  Seeing that it has an A2 non removeable baffle I am curious if the #2 drill trick will work for me.  I already put in a K&N filter but I haven't pulled the snorkle out yet.  

This is my first TT post.  So far I love the work you have all done here.

Hey! Same as me! Just got my '95 Baja there last weekend.
72,500km on the clock when I got it. New tyres, chain & sprockets, plus new-ish wavy discs.

I'm in Dublin, Ireland btw...

[99beast TT Newbie]

My ride is a 2001 XR400 and I never heard of Gordon's mods till I read this post tonight. My exhaust modification is a 1996 style baffle with a Thumper Racing insert (they are not in business anymore)  I can easily pass the 96 decibel sound test.  Uni air filter.  55 pilot and 168 main and tapered needle.  I ride a lot of technical stuff in the rocks and it works great.  14:45 sprockets.  I weigh just over 250# ready to ride and my top end is 75mph.  Even though this bike is old technology, you can't beat the reliability and it will take you anywhere you want to go until you get past 11,000 ft elevation.  I would buy another one if they still made them.

[Child TT Member]

Vegasdirtrider said:

I would suggest replacing your stock carb with a 36mm Mikuni, this will solve all your carb problems and will increase your overall performance, good luck.

A 36mm Mikuni like the one off of an 05 DRZ400SM? I have the stock carb which is a 36mm Mik that I trade out for a FCRMX carb, so if that'll fit I'd love to stick that on the XR!

[Texas XR TT Newbie]

First, thank you for everyone's comments on this site. Good information and help for all levels of riders.

Second, I did most of the Gordon mods this week on my 02 which included the three holes in the stock exhaust, Uni air filter, snorkel removal and jetting to a 158 / 60 setup.

My results were very noticeable. It starts easier and throttle response is much better! Thanks again for all the info!

Question: I am new at this so, how do I tell if my ride is running rich or lean? I may need to adjust the jetting again, but how do you tell? What are the symptoms of each?

[J13 TT Newbie]

Been searching high and low for the baffle mod pics.

Riding a 97' XR400R with original baffle (not sure if its for my 97' model) without spark arrestor.

after some close look @ the baffle, i noticed even if i drill 3 holes as mentioned in gordon's mod the middle (bloated) section of the baffle will not allow the any airflow to the 3 holes.

will appricate if anyone can provided the pictures of the modded baffle removed. bet there are still people out there still lost with the mod.

[red47403 TT Bronze Member]

J13 said:

Been searching high and low for the baffle mod pics.

Riding a 97' XR400R with original baffle (not sure if its for my 97' model) without spark arrestor.

after some close look @ the baffle, i noticed even if i drill 3 holes as mentioned in gordon's mod the middle (bloated) section of the baffle will not allow the any airflow to the 3 holes.

will appricate if anyone can provided the pictures of the modded baffle removed. bet there are still people out there still lost with the mod.

J13-
I believe the baffle mod is for the 98 and up XR4. The 96 and 97 have a more favorable setup because the baffel insert can be removed. I've heard of several people ordering the baffle from the 96/97 models and installing them on the newer models. The baffle insert is held in with one screw through the exhaust tip. Remove it and it will open your exhaust up. Most people reccomend leaving the spark arrestor installed, but if yours is already removed, oh well. Look at a schematic diagram on an OEM Parts finder (www.bikebandit.com or similar) and you will see the 'Tail diffuser'. This is the baffle insert.

This information is from what was done to my bike and from what I recall from reading tons of threads. Please someone correct me if I'm wrong about any of this.

When I bought my '97, the previous owner had already removed the baffle insert and the spark arrestor and I've been pleased with it. Not too terribly loud either, IMO. Good luck

[Old Brooklyn Boy TT Newbie]

Pull the plug. If dark and wet, Rich if Light and ash like, lean.

[t3lbbtx TT Newbie]

Mikuni w/Accelerator Pump What size to get for '02 XR400?
Sudco      TM 36-68
Al Baker's   TM 36-50
TT             TM 36-54?
I just want to bolt it on.
No housing mods unless absolutely necessary.
Thanks for this thread.Helped me alot over the years!

[pacree TT Silver Member]

t3lbbtx said:

Mikuni w/Accelerator Pump What size to get for '02 XR400?
Sudco      TM 36-68
Al Baker's   TM 36-50
TT             TM 36-54?
I just want to bolt it on.
No housing mods unless absolutely necessary.
Thanks for this thread.Helped me alot over the years!

You want the pumper from XR'S Only, comes with cables and ready to bolt on. Just tell them your setup, location (elevation) and wait for the Brown truck to come. Great mod, you'll love it.

[t3lbbtx TT Newbie]

Yeah everybody says Al Baker's is the best way to go,but I wanted to support TT,too.I even went so far as to ask Al's why they are the best.Their reply was that they haven't raised their prices in 5 years.
The XR400 already comes with push/pull cables.
Will the stock cables not fit the pumper carb?
Thanks,t3lbbtx

[pacree TT Silver Member]

t3lbbtx said:

Will the stock cables not fit the pumper carb?
Thanks,t3lbbtx

Well the XR's Only carb comes ready to rock with cables and all. No one else has the carb setup they have. You can get a pumper other places but to get it to run right takes work. Nope the stock cables are completely different from the pumper cables. When I put mine on I ran the cables the same route as the stock cables with no problems. No problem.

[XDINOX TT Newbie]

Hey has anyone tried to drill 3 to 4 5/16 holes, instead of 1/4 holes? I can get a 5/16 bit down in without touching the sides on my stock 2004 exhaust tip and would still be able to plug them if needed, just curious!!

[schrode Get Help Now]

everybodys suggestions are awesome and definitely useable.  keep in mind baby steps.  don't do too much too fast.  try all mods in a variety of conditions before moving to the next.  temp. and humidity can make a difference as well as altitude.  i regularly ride in a 500-5000 ft. range and anywhere from 95 degrees and 10 percent humidity to 35 degrees and 80 percent.  sometimes middle of the road is  best

[XR400rthebest TT Member]

hey i have a 2001 xr400r with a white brothers slip-on e series with stock headers . so did grinding out the head pipe help with performance and if so what else did you have to do to any part of the bike?

[partyman66 TT Bronze Member]

Holy Crap.... Gordons mods made a gigantic difference to my XR250.

I'd done some of my mods in phases, and not all at once.  I think the biggest individual difference maker was the Airbox Mods... meaning UNI Filter and Snorkel Delete.  I'd been riding with the UNI filter for quite some time, but I noticed a very significant difference when I pulled the snorkel.

After the header weld grinding, 135/48 jetting, UNI Filter, Snorkel Delete, and Sound Baffle Delete... the bike is much faster and more responsive(and obviously much MUCH louder).  My rear tire, which hooked up fine for me with just the UNI Filter for a mod, all of a sudden is completely useless and spins pretty good in the first 4 gears without using the clutch and just goosing the throttle.  Before the mods, I was lucky to do that in first gear.

I suppose that when I put my new tire on in a few days, the front end will actually come up under power for once since it'll hopefully have some traction.

The bike also seems to throw a lot more heat now, so I'm going to have to keep an eye on that and maybe get one of those oil dipstick temperature monitors to make sure it doesn't get too out of hand.

[sameoldme TT Bronze Member]

red47403 said:

J13-
I believe the baffle mod is for the 98 and up XR4. The 96 and 97 have a more favorable setup because the baffel insert can be removed. I've heard of several people ordering the baffle from the 96/97 models and installing them on the newer models. The baffle insert is held in with one screw through the exhaust tip. Remove it and it will open your exhaust up. Most people reccomend leaving the spark arrestor installed, but if yours is already removed, oh well. Look at a schematic diagram on an OEM Parts finder (www.bikebandit.com or similar) and you will see the 'Tail diffuser'. This is the baffle insert.

This information is from what was done to my bike and from what I recall from reading tons of threads. Please someone correct me if I'm wrong about any of this.

When I bought my '97, the previous owner had already removed the baffle insert and the spark arrestor and I've been pleased with it. Not too terribly loud either, IMO. Good luck

I've been searching for PIC's of the perforated Exhaust, mine's an ´01
THANKS for the pics for anybody that has done this to their bikes..

[sameoldme TT Bronze Member]

I did the 3 holes with a 1/4" drill bit right next to the outlet pipe, it seems that I hit the jackpot on the hole location since I got before the baffling. I'll install it this weekend and post pictures I already have. About the sound difference I didn't do a before, so I'll try to upload a youtube video for look and sound...
THANKS!

[pyroman83 TT Newbie]

i have been thinking about doing Gordon's mods to my 2000 xr 400, only thing i was wonder is what gearing i should go to if im going to make my bike street legal? Im at stock gearing now. and with your drilling in the pipe what jets should i run if i live at 2500 ft and ride anywhere from 5000Ft to sea level?