Miss-Fire Blues

[dragonz]

Emailed MD about this, as I recall him having something similar that he traced to a wiring fault, but figured I would "put it out there" for you all to see if anyone has other idea's or suggestions for me to follow up on.

Been having a few issues with my rappy & thought I'd run a few ideas past you to see what your thoughts are.
My bike started misfiring during a race 2 months ago.
Blamed it on a carb coming out of it's manifold boot, but as I wanted some more go, pulled the motor down & made a few mods.
We ride mostly at low altitude, 0- 1000ft above sea-level (FYI)

I have CT sonic pipe with 16 discs
K&N proflow & no lid
Mild porting & port matching
stage 2 cam & springs
11.1-1 CP piston

Raced it 2 weeks ago (finished re-assembling the night before) & it still was missing, but wasn't as bad, so figured was just a jetting issue.
Did a plug chop & figured it lean (had 195/195 mains, & 22.5/22.5 pilots, 3 turns out on pilot air, CT sonic needles, on 4th grove from top)
put 200/200 mains & 27.5/27.5 pilot & screwed pilot air in to 2 turns out each.

The bike starts easily, & pulls away cleanly through bottom end, at low mid especially on part throttle it starts to miss.
If you gun it, sometimes it pulls clean, most times it will miss, & slowly accellerate.

If I get the revs up, it wants to go, but still misses.

eliminated the park brake cutout, grounded the reverse light wire (just in case as the feeling is similar to that at times)

played round with the bike at the track as it wasn't worth riding as it was.
lowered the needles the whole way (top grove for circlip) & seemed to be a bit better, but still not good enough to keep riding.

Tried another coil, no difference.

Do you think my problem is more likely to be jetting or electrical?
Any suggestions on where to check on the wiring side of things?
CDI failing?

If I replace the cdi keep to stock or go aftermarket?
Dynatec or AMR? or any other suggestions?

Thanks

[Mad Dog]

I replaced the entire electrical system and gutted the carbs....and somewhere along the line the problem went away.

It's not the cdi, or the coil.  Those were my first thoughts too.  Pickup coil is a good place to start.  See page 8-6 of the manual for a troubleshooting procedure.

[dragonz]

Started working through everything again today, figured I would go through all the electrics.
Had to take battery out to remove CDI & found one of the battery terminals was loose!
Here's hoping that I have found the problem!

[Krandall]

Cool, hopefully it's as simple as that.

[dragonz]

Nope, wasn't!
now waiting to get home to try new CDI & coil

[Mad Dog]

Doubt it's the CDI....it's usually one of those things that either works or doesn't.  The intermittent seemingly random pattern is more likely to be a wire short or some kind of interruption.  Hope you're buying used stuff off ebay and not new parts or you'll end up like me with 2.5 raptor electrical systems on hand and a half a grand into a problem that comes and goes like the wind.

If you haven't already I'd go through the harness with a fine toothed comb checking for broken/damaged/loose wires and plug connectors.

[dragonz]

Well, I wanted an aftermarket CDI for the better advance curve, so I got one anyway
AMR stage 3 & coil for $165 & free freight.

So, went through all the electrical connectors
opened up, cleaned with contact cleaner

Inspected the loom
all looked fine

Re-checked the carbs
decided the fuel level was too high on one & reset float levels
Decided that maybe the other carb might be letting too much fuel in, float/needle problem?
so replaced both had some spares already (got a set of carbs off ebay)

adjusted the pilot air screws in as I thought bottom end might be a bit rich.

Started & it runs sweet.
Will go out tomorrow & give it a really good thrash & see how it goes then!

[Mad Dog]

You fixed too much stuff now we don't know exactly what fixed it.

I have the AMR coil too, but not running their cdi.  Coil packs go out, coil wires go bad, plug caps go bad (these are the first three things I changed out, in reverse order, but they didn't fix my problem).

Good that you did the electrical tune up anyway, should help prevent problems in the future.

Here's a list of what I did:

Those of you who rode with me at SL might remember I have been having engine troubles.  Figured out it was electrical after some work and a timing light.  Lots of adjustments and checks were done but with no benefit or change.  Here are the parts replaced:

Replaced spark plug, quite a few times
Replaced oem plug cap with aftermarket ngk cap
Replaced oem coil, wire and plug cap with oem
Replaced oem coil, wire and plug cap with aftermarket monster coil/wire and NGK cap
Replaced aftermarket CDI with previously working oem
Replaced oem voltage rectifier with oem
Replaced oem stator with aftermarket Ricky Stator unit (including pickup coil)
Replaced oem stator side cover with oem
Replaced oem wiring harness with oem
Ordered new control housing (start button/headlight switch/run-stop switch/etc) but it hasn't arrived yet

And just for good measure;
Removed inline fuel filter
Replaced fuel lines 2x
Cleaned carbs 2x
Rebuilt carbs



I'm very happy you got this resolved dragonz, just wish I could have offered some specific help but as you see I struggled with it as well.

[dragonz]

Having finally found time to give it a proper run, it still isn't right, but is a lot better.
It will start sweet as
& mostly will rev cleanly, but not always (1/4 times approx)

The thing that made the most difference so far has been lowering the fuel level in the float bowls.
When I re-checked the other day, 1 was at 4mm above the float chamber joint, the other 5mm (despite both having been set up at 3mm previously.
so I'm now about to lower them both to 2mm & see how that goes.

I think (like you) I have been battling more than one problem at a time
There had been moisture & dust in some of the electrical connectors
I have had some jetting issues
The float height had changed
CDI & coil?? don't know
replaced spark plug a couple of times too.

Was good t get on it & have it really pull well though, will be an animal once it is running really sweet
When I'm happy that there are no other issues then we go to the dyno

[dragonz]

With float-bowl fuel level at 2mm above the join I'm finally getting somewhere.
Just put the 200 (2.00mm) mains back in as was lean on top-end plug-chop.
Misses on part throttle in mid-range, but wants to scream like a mad thing at top-end.

The answer is to go through everything properly I think, & then do it again just to be sure.

Small electrical issues, combined with float-bowl fuel level going out of whack, combined with not properly sorted jetting = sick bike

[dragonz]

Well, if you change something & it aint working out, go back to basics.
Having solved the issues I was facing with regard to the bike running & pulling properly, I still wasn't happy with the jetting & it was still too rich in mid-range & lean up top.
Was running 2.00mm/2.00mm on mains, 25/25 on pilot jets, & Standard needles.

Now, I have a CT Sonic pipe, it came with needles, & Jets
The Jets it came with were waaay out of whack supposedly 170/175, they measured up at 1.90mm/1.95mm
(Stock is 140/145 & these do measure up at 1.40mm & 1.45mm)
So I had played with jets & needles & clip position & had a bike that went well.
ended up running 160/165 & the CT needles.

Now, when I put the cam & piston in, it was lean, & I threw in 190/190 because that's what I had right there, &  it was going ok, but not quite right.
Then it just seemed to get progressively worse in how it was running.
So you start to play.
By the time I had got to the bottom of my electrical connector/float setting/other fiddles that got it to run I had also changed my needles for stock to try & sort out being too rich in mid range somewhere along the way. It helped massively at the time & I figured that maybe I should have been running them all along...... (I was tired & frustrated ok)

Then, once it was running, it was waaay to lean top end, 190/190, 200/200.......I made a set of 215's & it was still too lean at top-end, but now waaay to rich in mid-range.
Thought, hang on, those are VERY big jets for this bike/carb combo & so I looked back on-line at what others were running.
For my build, 170-180 on the mains, & either CT or Dynojet needles.

Right, I must be waaay out of line then, so lets put that back in it & see what gives.
Did needles first.
Started & ran through into mid-range, then any more throttle just died (lots of gas now!)
bought jets back to 190/190, still rich at top-end

So now running 175/175 & seems pretty good.
170/175 was just a little too lean still.
I have made a few mods to my head so the even sized jets work pretty well.
You know that piss-arsed little hole from the left head port into the centre valve, I put an 18.5mm drill through it! Then tidied up the ahape into & out of it with a die grinder.
Seems to have improved things significantly (now the f**ker is running properly)!

So, if you have a problem, start by getting back to basics.
Make your jetting match what is working for someone else, & if that doesn't fix the problem, look elsewhere to fix it.
I was in fact masking the real problems slightly by the changes I had made to my jetting.

& I can also tell you that the standard needle will not flow any more gas past it at full throttle, regardless of the main jet size, anywhere above about 1.70mm jets.

The needle does have a significant effect on top end!

Good luck to anyone else having this kind of problem.
Now, I am finally ready for the dyno, pity I am away for the next 3-4 weeks

[AJ RAPTOR]

you know theres a guy out here that will dyno quads for $50 your only problem is getting the quad here hahahahaha might not be worth it for ya

[dragonz]

Nice,
sadly the dyno will cost me somewhat more than that.
Still, 300 notes is money well spent if it means I'm getting the best from my motor.

The sad thing is, I'm already thinking about my next build, & still haven't finished this one.............LOL

[AJ RAPTOR]

Nice,
sadly the dyno will cost me somewhat more than that.
Still, 300 notes is money well spent if it means I'm getting the best from my motor.

The sad thing is, I'm already thinking about my next build, & still haven't finished this one.............LOL

yeah I'm gonna talk to the guy with the dyno once i get the raptor going and see if he can book me another date to put the rapto ron it as it broke in 2007 2 days before it was to go it at the start so it would be nice to get it on this summer and hell $50 to dyno and get the gas sniffers put to it aswell for tuning hell yeah im not gonna complain about it.

[dragonz]

Well, the misfire came back!

But, this time I got it sussed.
There was a couple of wires sitting adjacent to eachother feeding into the cdi.
1 was black, the other white with a red stripe.
There was a patch on the insulation of both that had been rubbed!
The bike would start sweet, every time, but as the revs rose, it would start to missfire!
The 2 wires were shorting to eachother, not badly & not a complete short, but the damn thing was determined not to run well.
Seperated the wires & repaired the insulation with some high voltage splicing tape, volida, no more missfire!

the wires were nothing much important, just the main earth for the cdi, & the feed from the ignition pickup............LOL

The lesson, if you have a problem, unless you find something specific & fix it, it will probably return, at the worst possible moment.
Mine did, while wheelieing through a swamp!