Spark plug resistor removal--worth it?


13 replies to this topic
  • Owyhee

Posted April 01, 2007 - 02:03 PM

#1

I've been following a thread on the XR250/400 forum about removing the resistor in the spark plug boot to make a hotter spark (or whatever).

My 600 can be a difficult starter when it's cold out; this is supposed to make it easier to start.

As this is a free mod and completely reverseable I'm going to do it anyway. I have this whole week off of work if I choose and need an easy project to fill some time.

What is the forum's thoughts/experiences with this?

"O"

  • Kawabuggy

Posted April 01, 2007 - 05:26 PM

#2

I have read in another thread here about doing that mod... I too am interested in what the benefits of this move might make. If you try it, and like it, please let me know as I will follow suit.

  • Owyhee

Posted April 01, 2007 - 07:43 PM

#3

I have read in another thread here about doing that mod... I too am interested in what the benefits of this move might make. If you try it, and like it, please let me know as I will follow suit.


I'm thinking of a "scientific" way to do it. The bike is a 4-5 kick starter whrn cold (40-50 degrees) although on the first few kicks it "snuffles" if you know what I mean. Once it starts running it's a one-kick starter.

I'll let you know my progress and if my POS HP camera cooperates I'll take some pics too.

"O"

  • creeky

Posted April 02, 2007 - 03:21 AM

#4

I have done this mod to every XR I have owned and to be perfectly honest, I can't tell the difference in starting or performance. The reason I do it is because if the resistor fails, you are sitting in the middle of Podunk with a dead bike. Although it is not common, I personally know of two failures of the resistor, once when a friend lost a race due the resistor going bad and another when another friend's bike suddenly starting running badly, popping, backfiring and refusing to rev up. In both cases replacing the resistor with a steel rod fixed the problem.

  • Kawabuggy

Posted April 02, 2007 - 05:02 AM

#5

Is there any known way to test the resistor to prove whether it is good or bad?

  • Jeff@TheQuadShop

Posted April 02, 2007 - 06:37 AM

#6

What size screw is used and at what lenght does it need to be?

  • Zappa

Posted April 02, 2007 - 07:39 AM

#7

Is there any known way to test the resistor to prove whether it is good or bad?


A Multimeter (set to resistance) or Ohmmeter. Put the two contacts on the ends of the resistor and the usually read from 3k - 6k Ohms.

A steel rod or other conductive material would measure around 0.1 - 3 Ohms for a comparison.

What size screw is used and at what lenght does it need to be?


About a 4mm diameter bolt about 3/4" long works fine.

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  • TheCure

Posted April 02, 2007 - 11:55 AM

#8

I tried this mod out last summer on my 1993 XR 600. It made it HARDER to start when removed and replaced by the coathanger. I put it back in and it started easier with the resistor in.

Now, conversely I removed it from my FILs XR250 and that thing DID start easier.

:bonk:

  • Kawabuggy

Posted April 02, 2007 - 11:58 AM

#9

I just tested my resistor and it ohms at 5.67. I guess it is good.

  • Owyhee

Posted April 02, 2007 - 02:28 PM

#10

Well, the verdict is in: The bike still won't start with or without the resistor mod.

When I kick it fires three times--not two and not four--three times, then stalls. It's done this since I got it and it pisses me off. The only way to start it is to roll start it and it fires right off.

I've had 12 or 15 bikes in my life including some notorious hard starters (1984 XR350R and 1985 XT600) and no bike has ever pissed me off this much. I'm thinking of selling it and getting a KTM or Husaberg.

Aside from drop kicking the carb into traffic and getting a pumper carb, what's a boy to do?

"O"

  • Kawabuggy

Posted April 02, 2007 - 04:23 PM

#11

It sounds like you want to give up-DON'T! When you finally figure it out, it will be a simple thing. Plus, when you post back here, other people will have one more thing to check when they experience similar situations.

  • RTSinDallas

Posted April 02, 2007 - 11:26 PM

#12

I did the mod using 6 gauge copper wire. I also installed an irdium plug. And I put in a bigger pilot jet (a 68 I think) anyway it is a 1 or 2 kicker now. I do think that the condition of your stator probably dictates how much improvment, if any, you will see. Also adjust your valves. If they are tight it may effect starting.

RT

  • prockish17

Posted April 03, 2007 - 07:18 AM

#13

I know you all hate hearing it over and over but can we say edelbrock. Go ahead and say it three times real fast edelbrockedelbrockedelbrock. Best 400 bones ever spent. I only got mine because of starting. Lots of other bennys but getting rid of the age old 4 stroke carb which design hasn't changed since the 70's seems smart to me.

  • Jeff@TheQuadShop

Posted April 03, 2007 - 08:04 AM

#14

Actually can you say.......FCR-MX :bonk:





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