wr400 question


19 replies to this topic
  • Drifterke

Posted April 22, 2008 - 04:55 AM

#1

Hi guys,

I have been reading a bit on this forum but i never posted anything yet.
I have a wr400 in supermoto trim.
There has to be something wrong with this bike because i have sprockets 14/50 and i cant wheelie on the throttel. My brother rode 1 yesterday and that one could wheelie in 3d gear on the throttle with sprockets 14/43 or something.
My bike had a new piston and everything not so long ago so that cant be it.
When i open the gas fully from idle the bike sounds like its gonna die on me :thumbsup:

Sorry for my crappy english i'm from belgium ......

GrtZ Drifterke

  • matt4x4

Posted April 22, 2008 - 10:29 AM

#2

Accelerator pump and jetting I would guess - get that dialed in and you're golden.
If you throttle it and it chokes to nothing, your AP squirt is timed wrong or the diaphram is broken.

We need more details to do more diagnosing...

  • Drifterke

Posted April 22, 2008 - 12:01 PM

#3

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accelerator pump is ok i guess, diaphragm is not broken.
I think the bike is getting too much fuel by the looks of the spark plug ???

  • matt4x4

Posted April 23, 2008 - 07:03 AM

#4

did you do a plug chop or just pull it after running it a bit?
the color on the plug insulator looks ballpark good
Yes, you've got wetness, but depending on how you ran the bike before pulling the plug, that can be normal.
use a new plug, properly gapped to do a plug chop
To do a plug chop (which shows where your main jet is (lean/rich) you have to ride under load (hills will work) top gear wide open and kill the engine, pulling in clutch and chopping the throttle at same time.
Pull teh plug and read it.
That'll give you a good indication of your main jet.

To check your pilot jet for rich/lean, start bike, let it warm up, ride it for 10 minutes, shut off, now set your air screw to about 1/4 from seated, start the bike set the idle to smooth, lowest rpm but so it won't stall out - turn the air screw out until the rpms go up to the maximum attainable, verify this and do it SLOWLY since it always lags a bit behind.
After you've shut off the bike, count the number of turns to get the air screw seated lightly, if it's more than 2 turns you need to go bigger on the pilot jet, if it's less than 3/4 of a turn you need to go smaller, if it's between 1 and 2 your jet is fine and your problem could be dirt in the carb.

Once the right pilot jet is in, turn the air screw to 1/2 a turn out, start bike, and adjust air screw small amounts (1/8th of a turn) at a time until you have the crispest throttle response between 0 and 1/4 throttle (don't crank it, just blip it lightly)., it should respond nicely and drop back down fast, no hanging.

That should do it for the main and pilot jet.

If your bike bogs when you crank the throttle it's the AP that's out of timing and needs to be adjusted.

  • byggd

Posted April 23, 2008 - 11:37 AM

#5

Great info Matt! I think I just learned something :ride: Question though, why would you need to be in top gear wide open to do the plug chop test? Wouldn't any gear do as long as the upper RPM are reached with a load? :thumbsup:

  • Drifterke

Posted April 28, 2008 - 08:59 AM

#6

small update guys:

I took the carb off, cleaned it and gave it a good blowjob :p
There is a 62 pilot jet and a drilled out main jet in there.
I put that thing back on with the fuel screw 2 turns out.
It wouldn't start unless the hot start knob was out.
So i figured it was way too rich, took out the air filter and it started first kick :eek:
It rode better also without the airfilter.
I think i'm going to get some other jets tomorrow and put in a 45 pilot jet and a 172 main jet. What do you guys think ???


Thx JefF

  • byggd

Posted April 28, 2008 - 03:28 PM

#7

a drilled out main jet in there


Bingo! I think you found the problem!

  • Drifterke

Posted April 29, 2008 - 06:08 AM

#8

****ing hell, i put in a 165 main and it still runs like shit

*edit*: i calmed down a bit and i took it apart again and i saw this=>
http://users.skynet....010/motherf.JPG

I guess this was the problem all along ?????? We won't find out untill i've got another one in there. I'll order one tomorrow

  • matt4x4

Posted April 30, 2008 - 03:56 AM

#9

you really don't need to buy a new gasket - for what it's worth, it's probably ok to buy one for the long run, but for further troubleshooting, I would have just put some sealant on the tear for now and continued on.
I don't think that would have caused your continuos issues though since it's on the airbox side of the carb and would just allow a minute amount of extra air in (if at all).
Your main jet might be too small now as well as the 45 pilot since you dropped form a whopping 62.

As for being in top gear flat out for a plug chop - it's pretty tough to do on a good day with these bikes), so I'd think 3rd or 4th on a hill would suffice.

  • Drifterke

Posted April 30, 2008 - 09:50 AM

#10

i didn't change the pilot yet. i'll put this thing back together with the 172 main jet in and do a proper plug chop.

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  • Drifterke

Posted April 30, 2008 - 11:42 AM

#11

me again,

another thing is, i can keep pressing the kick down and down without having to use the decompression lever. This means the valves need to be set right? It can't be the piston cuz i have a new one in there...
Should i try it myself of just get it to the dealer ?

  • byggd

Posted April 30, 2008 - 03:56 PM

#12

me again,

another thing is, i can keep pressing the kick down and down without having to use the decompression lever. This means the valves need to be set right? It can't be the piston cuz i have a new one in there...
Should i try it myself of just get it to the dealer ?

You should have mentioned that in the first place :eek: Three things I can think of. 1) The decompress is stuck open 2) Valves are not closing (need adjusting) 3) Rings are shot. Most common is the valves need adjusting. Pull the valve cover and take a reading.

  • matt4x4

Posted May 01, 2008 - 05:21 AM

#13

Shimming valves is a piece of cake, do it yourself.
Pull the cover, set engine to TDC, TDC is where the vertical line lines up with the notch mark AND the lobes on the cams point outwards.
measure your gap, if there even is one, draw out a top view pic of the valves (I use 5 circles, 2 on left, 3 on right), inside the circles I write the current shim size (under buckets), beside the circle I write the current gap.
From there, you can cross reference the chart in your manual for both intake and exhaust to determine the proper shims required.

NEVER mix up your buckets, they may have slight variances in tolerance which affects shimming.

If one or two of your valves is so tight you don't have any clearance, try taking the smallest of your shims and replacing the one in that particular location to see if your can get a reading, otherwise you'll have to blindly buy a few smaller shims to do trial and error shimming until you can get a reading - making your purchase more expensive due to the extra shims you have to buy.

  • Drifterke

Posted May 01, 2008 - 05:23 AM

#14

i took a reading :eek:

i dno if these results make any sense but here they are


0.20 0.33
0.20 0.18
-----0.12
------------------ www wwww <~ sprockets on camshafts :p


the cam with 2 valves is out and the cam with 3 valves is in right ?

  • matt4x4

Posted May 01, 2008 - 10:19 AM

#15

yes, 2=exhaust, 3=intake

.200 on the exhaust is just a tad tight, same with the .12 on the intake, the .33 on the intake is WAY out (but on the wrong end of the scale) - unless something is making it stick open from the cylinder side....

none of those numbers should affect starting and/or running.
Try looking into where your carb connects for anything abnormal.....if you can't see anything, it might just be time to pop the head off...man, what a pain this si turning out to be for you.

to make you feel better, mine's got bigger problems right now!

  • Drifterke

Posted May 01, 2008 - 11:32 AM

#16

and thats not all

on the intake side there is only one spacer ( or hower you call those small round thingys) with the size on it. The others have nothing on them. Can i measure these somehow? I don't want to take the head off, it just has been off to put a new piston in. It has to be something else....( i hope to god)

thx guys for helping me get through this...

  • matt4x4

Posted May 01, 2008 - 11:55 AM

#17

Spacer is actually a SHIM
Did you check both sides of them or just look onto them as they were in place.
The sizes do wear off with use. - some of my my 184's read 84
A micrometer should work (digital preferred of course), just measure the thickness and compare it to the one you can read - I haven't done anything like that before though, but I'm fairly sure the number on the shim is NOT the actual thickness, I believe it's a variance - sort of like a blank would be a standard reference size spacer being 0 and then .184 (example) mm over that size.

  • Drifterke

Posted May 02, 2008 - 11:04 AM

#18

lol this is just ridiculous.
i was reassembling the crankshafts and one of those half circle seal rings fell into the engine and i cant see it anymore. I GIVE UP i'm taking it to a dealer tomorrow or next week i'm fed up with this thing.......
i'll let you guys know if he finds anything.

  • matt4x4

Posted May 02, 2008 - 11:51 AM

#19

Well, he better find that half circle - use a telescopic magnet - it wouldn't have gone too far - the head's not open to anything else from up top...

Don't give up, look at mine right now - it should provide inspiration for you!

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  • byggd

Posted May 02, 2008 - 02:20 PM

#20

Well, he better find that half circle - use a telescopic magnet - it wouldn't have gone too far - the head's not open to anything else from up top...

Don't give up, look at mine right now - it should provide inspiration for you!

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No wonder you have so much time to post right now :eek:




 
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