[Raptor46]

Hey guys, new member here. I've read many many threads here regarding my topic but I just can't win and get this thing started.

It's an '03 raptor that had the whole motor rebuilt by a reputable engine builder in my area. Stage 2 cam, bored .60 over and has a aftermarket CDI. It's been sitting for several years. After engine was done, we put it back in and it ran horrible which was likely due to the carb settings and or the clutch and parking brake sensors which I didn't know about then.

So put a set of aftermarket carbs on, main jet 165/170, 25 pilots and 2.5 turns out on the fuel screws and 3rd spot down on the needles. Under 1000' above sea level.

All it does it crank and crank then loud backfire then cranks more. Tried all kinds of stuff and made sure to use fresh gas, triple checked the boots were all the way on, replaced spark plug, verified spark, cleaned the carbs 3 times even though they're new! Checked the valves, timing you name it.

THEN, either by pure coincidence or because of this I pulled in the clutch making sure to engage the sensor and it started! High idle but sounded great, hit the gas and had great throttle response. Turned it off and tried again and never got it to start again.

I read about the sensors and disconnected the two of them above the radiator. I thoroughly cleaned the oem carbs, put them on and tried again.... nothing. Now I'm not even getting the backfire. I know gas is making it into the bowls of the carb, I sprayed starting fluid in the spark plug hole and still doesnt start. Just did a quick compression test and it was 135psi with everything on it.

PLEASE someone help me figure this thing out 🙏

 

[Sixpack577]

Keep the oem carbs on it.

@QuadManiac

Quoting him will give him an alert to see this.
He can best direct you what to do next.

 

[Raptor46]

Ok, I did put those back on and that's where I left it. Thank you for tagging him, appreciate it.

 

[cerino2000]

Is the plug soaked? Bypass any of the nannies temporarily to take them out of the equation. When turning it over does it sound like it should? No hard hesitation like your timing is off?

 

[Raptor46]

Is the plug soaked? Bypass any of the nannies temporarily to take them out of the equation. When turning it over does it sound like it should? No hard hesitation like your timing is off?

No, the plug isn't really wet. Surprisingly. The bowls are filling up though, what would prevent the gas getting to the plug? I did notice a little smoke coming out of the muffler as I'm trying to start it. Turns over as it should but I notice a sort of whine noise as it's turning over, possibly the starter motor. 🤷‍♂️

 

[Sixpack577]

Have you checked to see if it's firing?
It doesn't sound like it.

 

[Raptor46]

Have you checked to see if it's firing?
It doesn't sound like it.

I checked the spark and it's great... Every time I check it it's bright. I even put a new plug in and still looks the same, easy to see spark.

 

[Sixpack577]

135 psi is also low, it should be 150-190ish.
I cannot say either way that 135psi would be too low to run, but it should be much higher, especially on a new rebuild.

 

[Raptor46]

Ok, thank you I thought it was ok but I'm not too familiar with these engines.

 

[Sixpack577]

You can download the pdf service manual in the Stickie section.

 

[QuadManiac]

Welcome to the forum!

Let's see if we can make any sense (not in any specific order) of what you have described in nice detail.

1) Return to the original carbs - I assume you have replaced them with the <$100 eBay carbs and they are worthless... perhaps 100 forum members have described their failure trying to get these carbs tuned properly. They are very poor Chinese copies of the originals and appear to have terrible tolerances. We always suggest that you thoroughly clean and re-install the original OEM carbs. The copies are good for supplying spare parts, just not any that tightly control flow of fuel or air.

If this is NOT the case, then ignore #1... just needs to be said to get us on the same page.

2) Make sure the green/white stripe wire (reverse switch) is grounded to frame or negative battery terminal and green/yellow stripe wire (parking brake switch) is disconnected.

3) The clutch switch (black/yellow stripe) simply allows you to start the engine when the quad is in gear - it has noting to do with spark, only starter operation - this is unrelated to your problem.

4) You have not mentioned your exhaust or airbox mods. The jetting you have described (165/170) is typical for open airbox and full exhaust system. If you're airbox is stock then you are WAY too rich - but probably not your primary issue.

5) You made no mention of needle type - having a non-stock, open airbox just about mandates the need for aftermarket needles (Dynojet are the only ones available now) - you will have a very hard time getting the three circuits of the carbs to work together smoothly without these needles - but this is not likely the cause of your lack of firing.

6) Your measured compression is plenty, perhaps a bit high - the 660 has an auto decompression mechanism that drops compression at starting RPMs. 90-100 is not uncommon. Stock compression is 9.5 to 1 so 135 is quite good.

7) IMPORTANT - Since you have not been able to make the engine fire and run briefly with starting fluid, the carbs are NOT your primary issue. With starting fluid it should sputter and try to run even there were no carbs and you sprayed the fluid straight into the intake manifolds!

8) Verify the integrity of the stator - again, if you have good, continuous spark, this is not an issue... but verify spark! If none, or intermittent - then try unplugging the regulator/rectifier to see if it returns. Then measure the resistance of the stator windings (not the 3 white wires) to verify they are close to the measurements as described in the manual.

NOW - I would first suggest loss of spark - but you claim great spark. Make darn sure of that (especially because of your one 'miraculous' start up and run.) Spark is still my first suspect.

My second suspect is ignition timing - if the woodruff key is missing or sheared then you can have great spark, just at the wrong time because the flywheel is able to rotate on the crankshaft. Each time a backfire occurs, very high rotational stress occurs at the key - enough to shear it. Then, with the flywheel slipping a bit each time you try to start, it is possible to randomly be in the proper location and, voila, it will start and run, only to slip away again after the next significant angular acceleration. This fits best with your explanation of symptoms so far even though I still suspect spark. Two ways to check flywheel clocking:

1) if you have a good old timing light, put the clamp around the spark plug wire, and power connectors to battery. Then remove the small inspection port from top of the left side cover to uncover to edge of the flywheel. Crank the engine and look for the "H" mark on the flywheel to be illuminated by the timing light.

2) Remove spark plug and insert a dowel or screwdriver into the hole (be gentle, don't scratch the piston!) Remove the center inspection plug from the side cover and turn the crankshaft CCW, then back and forth until the piston is at it's highest point. Then look through the upper (smaller) inspection port at the flywheel edge for the "I" mark denoting top dead center.

If either of these misses showing the proper marking, the flywheel is likely loose on the crankshaft.


One more possibility is an error in cam timing, but your one 'miraculous' startup and run somewhat discounts this... so I would ignore it unless nothing else pans out.

OH, one more possibility - did you ever have it running (long term, successfully) with the new CDI? It could be the issue. Do you have the original? A quick swap will tell you if this is the issue.

Sorry about writing a novel. Good luck and keep us informed of your progress!

 

[Sixpack577]

135 psi is also low, it should be 150-190ish.
I cannot say either way that 135psi would be too low to run, but it should be much higher, especially on a new rebuild.

I did not consider the auto compression release mentioned in Quadmaniac's post.
Sorry for bad info.

 

[Raptor46]

Wow, I'm blown away with the thorough and concise response QuadManiac!! I have to say, it seems you've earned that name quite well. Thank you so very much, I will get on it and report back!

Before I do, I want to mention a couple things. The airbox is stock with lid, the needles are OEM and the carbs are also back to OEM. I'm not sure if the oversized pistons helped increase the compression or not.

Regarding the jetting, would you have any suggestions for me to try? I wasn't sure with the bigger pistons and stage 2 cam if that would be good but was reading another post about everyone's mods and jetting. Kinda went with the richer setting.

Your "novel" is welcomed and you definitely helped get me rejuvenated to get it running. I'm going to verify the reverse switch is grounded & parking brake switch is disconnected. Then do the test for the crankshaft key. Thanks again!

 

[Raptor46]

I did not consider the auto compression release mentioned in Quadmaniac's post.
Sorry for bad info.

No problem, thank you again for your help!

 

[QuadManiac]

Thanks!

If your exhaust is also stock then you need stock mains - unless you have a full aftermarket exhaust where I'd suggest 1 or 2 sizes above stock. Regardless, you are currently way. way too rich... but, again, probably not your primary issue.

BTW, what's your elevation?

 

[Raptor46]

Full exhaust, so maybe start with 150/155?

Elevation is 400'.

 

[QuadManiac]

I would say that is a good starting point.

 

[cerino2000]

It can run on 135 if it was that. Get some Carb cleaner and give a shot to a carb and see if that makes it fire. That will eliminate the question of lack of fuel. You can run it temporarily without the airbox for testing. Also if you are in fact fat on the air fuel, no airbox might help you. Great idea above about the timing light.

 

[Raptor46]

I would say that is a good starting point.

I've been trying all sorts of things to no avail. Finally found the OEM CDI. Put it in and it STARTED! You were on to it! When I attempt to give it gas, it just breaks up, sputters and wants to stall. If I put the choke on, it sounds better and will at least let me rev it up some. That tells me that it's too lean, even with the larger pilots and jets. I'm thinking first step is to try turning the fuel screws on both...

 

[Raptor46]

The other thing I'm noticing is the throttle is rough ONLY when running, almost like only operating one carb. I checked for smooth operation and checked that they both look balanced before putting them back in.