96 XR400 CDI on the XR650R.


19 replies to this topic
  • Thumpage

Posted May 08, 2008 - 08:10 AM

#1

I bought a used 1996 XR400 CDI, (actually two) and a 96 XR400 flywheel, since the 96/97s seem harder to come by and are more expensive. These were very reasonably priced so I bought the trio.
As has been discussed around hear before and what I have found elsewhere to substantiate the info between the 96/97 & 98-2004 year models, the 96/97 North American CDI version is supposed to have further advanced timing over the 98 & newer versions. This makes the 96/97 version, the one to have. The euro/Aussie bikes kept with these 96/97 versions. The flywheels are different as well between 96/97 & 1998-2004 models.
As for the XR400 flywheel, I got it mainly to look at the size difference and position of the pickup tab compared to the 650R. I also wanted to see how similar it is in general to the XR650Rs flywheel. I would be curious to compare notes with a 98-2004 year model XR400 as well, if someone wants to pull one & compare notes just the same.
I do have my flywheel lightened and I figure the 96 400 CDI is going to be a good synergistic addition to this mod..

I fitted the 400 CDI on the bike last night and ran it in the garage. I did not ride it out on the street. Even with it installed on the bike and just letting it run at idle and revving it up, you can tell the difference in how it runs. The first thing that I noticed and what surprised me, was that the bike actually runs a little higher in the RPMs at idle between the two CDIs. To be sure of this, I switched them back and forth about 3 or 4 times. I think what I am seeing is the slight advancement at idle is what makes this difference. Not only does it idle higher, it actually seems to run more evenly or rather smoothly or cleanly. I have to check it out further to see if when I lower the idle speed down to where it is with the stock unit whether it still seems to hold a steadier and/or crisper idle.
Now, as far as free revving when whacking the throttle open, it surely jumps up further into the upper revs. It does sound different up there. It has a sort of raspier crackling sound when it hits the upper revs and starts to come back down. By going back and forth with the CDIs, and going back to the stock unit, it sounds muffled and held back for sure in comparison to the "96 400" when it hits the upper revs. That's a given of course because of the rev limit being higher.
Now, the higher rev limit alone is not the real or priority benefactor for this mod.. It is for the advanced map timing it offers. So far, with the "96 400" fitted, it makes the bike [sound] like a crisper running machine.

The '96 400' flywheel's pickup looks to be positioned a little bit further forward in the flywheels rotation in what would seem to provide an earlier pickup signal, (maybe). Other factors may take into account, such as the relation of the timing marks. What is also noticed at a casual glance is that the pickup tab appears to be noticably shorter than the 650Rs pickup which appears it might translate to be a shorter duration. :eek:
More info. to come when I get the chance to pull my 650s flywheel and make measurements of both.

  • martinfan30

Posted May 08, 2008 - 01:34 PM

#2

Nice write up and test!:eek:

I just wish someone would figure out this for the L...

  • XR650L_Dave

Posted May 08, 2008 - 01:55 PM

#3

Nice write up and test!:eek:

I just wish someone would figure out this for the L...



All you need is a 12VDC to 200-300 volt inverter running at a few hundred hertz.

Just copy the plans and parts from the applications section over at maxim semiconducter.

I'm just too damn lazy to do it myself.
And too cheap to buy a XR600R CDI.

Dave

  • XRMANU

Posted May 08, 2008 - 02:10 PM

#4

I was wondering the same. I was planning on using a lighted XR400 flywheel.Because of the different pick up tabs ,I let lighten my 650R flywheel but it broke 2 week ago . It was milled down on the wrong place :p Don't touch the engine side to much,I learned it the hard way,this part cost more than 600 euros in Europe. :applause: It broke (mounted on my 650R supermotard ) on an off-road section while heavily spinning trought the corner. .. + 9000 rpm ,Yes I also have a XR400 cdi on it.

Posted Image


XR400 <-> XR650R flywheel.
Posted Image

I don't know anymore witch one is from the 650,the pic is take a while ago.( I think the right one) :eek: The 400 flywheel is from an Euro '97 model. Both flywheels weight 1875 gr .

Edit: the right one is indeed from the 650,I just checked.: tab 650: 30.8mm/tab 400: 24.8mm

Anyone used a 400 flywheel on a 650R before with or without the 400 CDI ? effects??

  • Thumpage

Posted May 10, 2008 - 07:25 PM

#5

XRMANU,

That is too bad about your 650R flywheel. I would imagine that turning down the back side of the flywheel's body material would make it too thin and that is what caused yours to break. What needs to be done is to turn down the diameter of the [weight] that is grommeted to the back of the flywheel. Mine was turned down to the edges of the grommet recessed holes. (Pic attached further below for reference)
The back of the flywheel body was turned down just a tiny bit. Then the outer diameter of the flywheel was turned down as well as the middle section milled down. Total lightening; 10.5ozs. (I have a past post on this). I have just filed away the excess 'ramps' that were left on either side of the pickup after the milling that was left over from before. I will submit a picture of the updated work when I get the chance.

I took pics of both flywheels side by side with angles showing the difference in the pickup positions while in what would be the same position on the crankshaft. The pickup on the '96 400 flywheel is further forward on rotation as well as all the timing marks. (We have to consider the different stroke of the two motors, amongst other things).
The two flywheels appear to be basicly identical in every other way other than the position & length of the pickup tabs and the timing/indexing marks.

O.K.,.. I tried the '96 XR400 Flywheel on my bike with the the '96 CDI fitted and the bike started right up and runs just fine with the combo. As a matter of fact it ran great, ('on the stand'). I did not ride it.
It idled great. It was smooth and had great response. It actually seemed to run even slightly higher at idle with the matching combo than with the '96 400 CDI alone. I also thought I noticed that the bike does idle just a little more steady with the full weight '96 XR400 flywheel than with the lightened 650R flywheel, (even with the '96 CDI fitted with it). It seems there is sort of two stages of idle speed above the stock setup, between the setups. There is the stock CDI & flywheel, as usual then stage 1) '96 400 CDI & 650R flywheel, a little higher at idle 2) The '96 400 CDI & '96 400 Flywheel combo, a little bit higher still, at idle. The differences aren't big, but noticable. At least from what it appears to me by switching back and forth. It seems there is about 150-200rpm difference from stock to stage 1 and maybe another additional, up to 100rpm with the stage 2 'combo'. :thumbsup:

With the full 400 combo, the bike seems to rev out characteristicly somewhere in between the stock CDI/650R flywheel & '96 400 CDI/650R flywheel combo.
I may just have to have this '96 400 flywheel lightened to see what overall effect the "Full Monty" combo setup could give.

One thing I still have to confirm is whether any portion of the 650Rs power is negatively effected when actually riding the bike. I wonder about the upper rev range power effect with the shorter pickup signal and longer stroke motor. This is if the two are even really relative to each other. :rolleyes: :rolleyes:
Anyone with some ignition knowledge and experience, feel free to chime-in with your thoughts & input.

Comparative pics:

Starting position - '96 XR400 flywheel at the back.
Posted Image

400 Flywheel pickup is advanced forward.
Posted Image

All 400 indexing/timing marks are advanced as well.
Posted Image
Posted Image

The backside of both flywheels - Lightened 650R flywheel at top.
Posted Image

  • Agent2

Posted May 10, 2008 - 07:36 PM

#6

Excellent post Rich (as usual). But I get confused easily, when you were swapping CDI's and noticing differences in sound and "crispness" were you still using the stock flywheel?

  • Thumpage

Posted May 10, 2008 - 08:08 PM

#7

Excellent post Rich (as usual). But I get confused easily, when you were swapping CDI's and noticing differences in sound and "crispness" were you still using the stock flywheel?


Yes, initially, (in my first post) I was using the XR650Rs flywheel and testing it with both CDIs back to back. Just to be clear, my bikes flywheel is lightened.

This second go around in my last post, I was mainly testing the two *flywheels* back to back with the '96 400 CDI in the bike. (My lightened XR650R flywheel & the '96 400 flywheel).
Note: From what I can tell & from the info. XRMANU has given, the stock '96 400 flywheel is the same weight as a stock, (unlightened) XR650R flywheel. The two flywheels in stock form are basicly identical. The only real differences are, the flywheel pickup lengths are different as well as their timing position on the flywheel.

  • XRMANU

Posted May 21, 2008 - 02:54 AM

#8

Any update on the use of the XR400 flywheel on the 650? :thumbsup: :rolleyes:

  • Ryanthegreat1

Posted May 21, 2008 - 12:06 PM

#9

What part number is the 96-97 CDI?

The 96-97 and 98-04 have two part numbers listed for the same part they are:

30410-KCY-671 $134.03
30410-KCY-761 $94.98

These are both CDIs and they are both in the parts list for 96 and newer XR400s. If someone could verify which is the correct part number that would be very helpful.

  • Ryanthegreat1

Posted May 21, 2008 - 01:33 PM

#10

Well looks like I may have answered my own question. The 2004 XR400 parts fiche shows only this part number for the CDI:

30410-KCY-761

This makes me believe that the other part number is probably the 96-97 spec unit.

Can anyone confirm or deny this?

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • XRMANU

Posted June 13, 2008 - 01:04 PM

#11

Any update on the use of the XR400 flywheel on the 650? :thumbsup: :busted:


:busted:

  • martinfan30

Posted June 13, 2008 - 01:14 PM

#12

:thumbsup:


Thumpage(Rich) has been real busy at work and not much time for anything.
Talked to him last weekend.

  • XRMANU

Posted June 13, 2008 - 01:44 PM

#13

Ok thx.Looking forward to the report of his test work with the 400 flywheel.

Btw: I replaced my broken flywheel with another from a 650.
They took 350gr off the new one,on a safe way this time..:thumbsup:

  • martinfan30

Posted June 13, 2008 - 02:43 PM

#14

Ok thx.Looking forward to the report of his test work with the 400 flywheel.

Btw: I replaced my broken flywheel with another from a 650.
They took 350gr off the new one,on a safe way this time..:thumbsup:


He said he still wants to do it, just doesnt know when.

  • J_T

Posted July 31, 2008 - 07:34 PM

#15

Bump, Any news? I'm building a big bore XR650R and was looking at aftermarket CDI's but when I saw something about the slightly advanced timing of the XR400 flywheel...I can't wrap my mind around what that could do for me? can anyone clarify how advancing the timing would benifit the XR650R stock or even overbored with Stage2? I spoke to my shop about lightening the flyhwheel but he talked me out of it. If I hear enough good reports I may talk him into it, but My bike will always be a 50/50 dualsport, not a SM..

Just a little bump for a good thread!

  • martinfan30

Posted July 31, 2008 - 07:37 PM

#16

Bump, Any news? I'm building a big bore XR650R and was looking at aftermarket CDI's but when I saw something about the slightly advanced timing of the XR400 flywheel...I can't wrap my mind around what that could do for me? can anyone clarify how advancing the timing would benifit the XR650R stock or even overbored with Stage2? I spoke to my shop about lightening the flyhwheel but he talked me out of it. If I hear enough good reports I may talk him into it, but My bike will always be a 50/50 dualsport, not a SM..

Just a little bump for a good thread!


I will be meeting Thumpage this weekend for a little vacay up in Tahoe this weekend. I will ask him about it.

  • HeadTrauma

Posted July 31, 2008 - 08:08 PM

#17

can anyone clarify how advancing the timing would benifit the XR650R stock or even overbored with Stage2?


Advancing the timing closer to the knock limit will increase responsiveness and power. Doing it to a stock or mild engine doesn't usually achieve much except forcing you to buy higher octane gas than before. A high compression and/or built engine may not be able to use more timing because of the increased octane sensitivity.

Something to consider is that the XR400's design inherently requires/allows more ignition advance. It has a smaller bore than the 650R and it revs higher. It also has a worse hemishperical chamber shape that needs more timing than the 650R's better pentroof design. I don't know how conservative Honda was with the XRR's timing curve, but it's possible that it won't really benefit from more advance. With many engines there is a point where more timing starts hurting power even if there is no ping.

  • J_T

Posted August 01, 2008 - 05:59 AM

#18

Advancing the timing closer to the knock limit will increase responsiveness and power. Doing it to a stock or mild engine doesn't usually achieve much except forcing you to buy higher octane gas than before. A high compression and/or built engine may not be able to use more timing because of the increased octane sensitivity.

Something to consider is that the XR400's design inherently requires/allows more ignition advance. It has a smaller bore than the 650R and it revs higher. It also has a worse hemishperical chamber shape that needs more timing than the 650R's better pentroof design. I don't know how conservative Honda was with the XRR's timing curve, but it's possible that it won't really benefit from more advance. With many engines there is a point where more timing starts hurting power even if there is no ping.


let me see if I interpreted what you said and if I understand by restating an over-simplified statement; Changing the timing is telling where in the stroke to fire, in the difference between the XR650R and XR400 in this case the XR650 fires after TDC and the XR400 fires closer if not almost at TDC? By advancing the timing it will spark sooner giving the gas expansion helping the downstroke of the piston sooner (at higher compression) than just centripetal force?

let me know if I'm grasping it? with my build I didn't go with 11:1 I i did the 10:1 because most of my fuel stops out riding are at farm stations where I can't always get quality fuel and I didn't want to HAVE to run race fuel?

I guess if some one WANTED to move the pick-up it would have the same effect? (like twisting a distributor on a V8?)


I can't wait to hear about the XR400 CDI!!! on these bikes!

  • HeadTrauma

Posted August 01, 2008 - 10:41 AM

#19

let me see if I interpreted what you said and if I understand by restating an over-simplified statement;

1.) Changing the timing is telling where in the stroke to fire,

2.) in the difference between the XR650R and XR400 in this case the XR650 fires after TDC and the XR400 fires closer if not almost at TDC?
3.) By advancing the timing it will spark sooner giving the gas expansion helping the downstroke of the piston sooner (at higher compression) than just centripetal force?

let me know if I'm grasping it? with my build I didn't go with 11:1 I i did the 10:1 because most of my fuel stops out riding are at farm stations where I can't always get quality fuel and I didn't want to HAVE to run race fuel?

4.) I guess if some one WANTED to move the pick-up it would have the same effect? (like twisting a distributor on a V8?)


1.) Yes

2.) Neither of them fire after top dead center, a least not in the context of Honda motorcycles. The timing "advance" numbers you see around here relate to degrees BTDC, or degrees before top dead center.

3.) The higher the advance, the sooner the combustion event is started, the higher the cylinder pressure is, and thus results in more torque and power. Fuel chemistry also plays a large role is this process.

Imagine a cylinder with a homogeneous air/fuel mixture and the piston is compressing it into the combustion chamber. This compression induces adiabatic and mechanical heating to the mixture(like how the outlet on an air compressor gets hot). Now the sparkplug fires somewhere around 25 crankshaft degrees before the piston is at TDC. Now we have a piston still compressing the mixture, but the burning and expanding flame front is also further compressing the unburned air/fuel mixture. If the spark happened too soon, the pressure and heat in the chamber can go high enough to cause the unburned air/fuel areas in the chamber to autoignite and burn extremely fast. The piston can't get out if the way fast enough and the cylinder pressure spikes dangerously high. All that energy is exerted on the engine's head, cylinder, and rotating/reciprocating assembly making the characteristic rattling or knock of a pinging engine. Race fuel is more resistant to this autoignition process, allowing more timing and compression.

4.) Moving the ignition pickup does not actually change the advance curve; it just shifts all the numbers by a fixed amount versus using a CDI with a different curve. It's like the difference between turning the distributor on a car engine and changing the shape of the advance curve with different distributor weights.

Exhaust gas temperature is also a good way to monitor ignition advance. EGTs will usually climb rapidly the later(more retarded) the spark plug fires. This is due to the late ignition and more burning fuel being sent into the exhaust. Advancing the timing does the opposite.

  • J_T

Posted August 01, 2008 - 11:00 AM

#20

... Now the sparkplug fires somewhere around 25 crankshaft degrees before the piston is at TDC. Now we have a piston still compressing the mixture, but the burning and expanding flame front is also further compressing the unburned air/fuel mixture. If the spark happened too soon, the pressure and heat in the chamber can go high enough to cause the unburned air/fuel areas in the chamber to autoignite and burn extremely fast. The piston can't get out if the way fast enough and the cylinder pressure spikes dangerously high. All that energy is exerted on the engine's head, cylinder, and rotating/reciprocating assembly making the characteristic rattling or knock of a pinging engine. Race fuel is more resistant to this autoignition process, allowing more timing and compression.


Thats very enlightening...I didn't realize the ignited fuel actually further compresses by burning... I assumed once ignited it begins expanding and is why I never understood or fully realized BTDC though i've seen it as a term?

I enjoy this type of information, I don't get much of it in the Health-care field.

I'm not going to try to move the pickup and won't fool with advancing the timing because We've always been taught that "The evil of good is better" (if i'm stating it right) as well with only one bike I'm not going to go changing too much just to experiment. I'll stick to tried and true methods (which is why I can't wait to hear about the XR400 CDI!!) until a later date when I can have a project bike and one to keep running!





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