drr 90cc backfiring!?

[raptorobbie]

Hi all, I have an 08' 90cc air cooled bike w/ DRR's quiet pipe for an exhaust. My main jet is down to a 105 or 102, and the pilot is a 38. Stock air filter attached right on to the carb. The engine is completely stock.

We were riding a couple weeks back in some real bad dust, and the bike lost top end to the point it couldn't make it up even slight hills. I tore down the carb and cleaned it, cleaned the plug too, but still no top end, so I stuck it in the trailer for the rest of the day. All the while, the bike seemed to be getting louder and it hit me on the way home that the pipe probably came loose at the head - which it did! So I blamed the lack of top end on the leak at the head.

Got it all cleaned (carb and filter) again and put the head pipe back on (lost one screw) yesterday. Fired it up, and still no top end. It just bogs down and dies if you hold the throttle open. If you let off it will recover until you hit it again. I tried adjusting the carb (pwk 24) to no avail, and after my brilliant carb adjusting now it spits and shoots flames out the exhaust tip!! Now it doesnt even have enough power to move itself before it just dies! Help HELP!!

Thanks!

[ww228king]

i have started to have the same problem with a polaris 90 sportsman.... When you rev it out, does it start to act like a rev limiter is kicking in? I am thinking it is the stater ...

[Nichols Atvs]

make sure all your wires are plugged together and no brroken wires. Check your stator for dust build up and you may need to raise your main jet . Did you put in a new plug and what color was the one you took out. Make sure you didnt over oil your air filter. Check your cvt out and clean it . is your oil injection working or unhooked. Do a compression check you could have over heated the engine and need to do the top end.

[raptorobbie]

plain and simple, this bike will not rev, and it has gotten worse since the ride - flames shooting out the pipe is a bad sign. It almost seems as if the CDI is bad?

There was no oil on the air filter

Has nothing to do w/ CVT

I will have to check dust on the stator

Bike starts just OK, will idle, but not for real long before it dies on its own (done that since day one).

I may return it all to stock and see what happens.

Keep the suggestions coming though, thanks....

[raptorobbie]

sorry couple more points....

yes, I'm still using the oil injection.

The plug looked pretty decent - a little to the rich side.

Wiring all seems to be intact w/ the stock tether switch bypassed.

Hello put a GROUND wire from your frame to your motor and back firing will quit. Mine done the same thing till i put the GROUND from coil to motor. It would not rev, idol ,and blew up a set of carbon fiber reeds. i suggest you try this. This is what it is IMO. Try and let us know. Thanks Toby

[Nichols Atvs]

Could be the cdi change it out .You should run some filter oil on your filter with an outerware if you run where its dusty to help keep the dirt out of the carb .Dont have to just a sugestion. Good luck

[riding4fun]

Make sure the rubber boot ( carb to intake) is not cracked.

And you say you cleaned the carb, did you fully remove the air screw and clean that out also. I had the same problem just after I took them to the dunes. I cleaned the pilot circuit and all other jets out and ran fine. The dirt builds up easily in there.

[raptorobbie]

Toby, I like the ground wire idea - I did check the ground to the cvt case just to make sure it was there. Just to be clear though, you said from "frame to motor", then you said "from coil to motor". Does the coil bolt to the frame? and that's where you attached ground on the "frame" side? Also where on the motor did you attach?? Thanks - not trying to be picky just dont want to yank out any more hair!!

Nichols - what type of air filter are you running - I was thinking of going K&N but I heard good things about the Uni's - definitely would/will be using an outerwear with either one.


Riding4fun - No, I didn't take the air screw all the way out - total novice when it comes to carbs - I did take the jets out, and clean them just not the air screw. What about the idle screw? does that come out too?? I'll check the boot as well.

Thanks everyone!

pull out one bolt holding on your coil place wire on bolt and tighten up then go to youe side case of cvt and pull out one of the bolt holding on the side case ,cvt side and place your ground wire there and see if that dont fix it. if not its a guess like we have been doing from the start then try Nichols idea and Riding4Fun or try theres first its just a suggestion and Good Luck with your machine. Thanks Nichols and Riding4fun for trying to help everyone out that needs help you guys are awsomw:D Toby

[bulldogfallon]

To fix a problem you should retrace the steps that got you into your issue.

If the quad ran fine with the previous jetting then you may have to clean out the carb, but not much else.

I think the carb may be a little big for that pipe though....

You could have pulled the cold air/dirt in through the leaking exhaust or through the intake and worn the down the exhaust side of the piston ring.


Have you checked your compression since the ride and did you reinstall an exhaust gasket?

[Nichols Atvs]

I like the unis and i have like 6 of them so i always have a clean one to use they are cheap and with the outerware work real good. Also like i said in my first post i think you should do a compression check .

[bulldogfallon]

We used to use only the unis as well...just be careful to watch for the boot to crack if the clamp is too tight..

K and N have a much stronger boot...

The uni usually cracks on the bottomside so it can be hard to catch until it is too late.

Like heath requested...get a compression reading

[marsrace2]

make sure the plug wire isnt loose where it screws into the coil, I had similar problem happen on an apex proshark. I found that the plug wire was worn where it goes in to the coil. if so you just cut the end of the wire off and screw it into the coil again.

[raptorobbie]

thanks for all the replies so far - all very good ideas and suggestions!

Just to clarify, the setup that I was running that day has worked very well in the past and worked very well that morning until we noticed the topend cutting out.

The problem is definitely getting progressively worse, which in my mind points to something that's dirty, wearing, or loose.

I dont have a compression guage - any suggestions as to where to get one or what type - thanks!

rob

[marsrace2]

you can get one at harbor freight for less than 20 bucks

[SMS]

try going bigger on the main jet if you have not got it fixed already. I see this all the time and it is usually to lean on main jet. I run a 125 mj with tube on air filter or just straight air filter 145mj. I hope this helps you.

[raptorobbie]

SMS - thanks for the input - like I said, my setup worked well in the past and was working well that morning - so either something came loose, broke, or too much dust in the carb eventually affected the compression.

Actually - it could be just a spark plug failing! I did have this exact thing happen on my boy's Blaster a couple years ago - it would start but not take much throttle before puking on itself....


I havent had time to wrench on it yet though + it gets dark too early w/ the time change!!!!

Also, I'm prepping for the worst - which would be needing a new top end, what would you guys suggest? My kid does not race - but may enter a scramble here and there, and is an excellent rider and could easily handle more power. I want to keep it simple - would buying a cylinder and piston from Hetricks be the way to go - is there enough bang for the buck + is it reliable. I want to stay simple and not get into needing race fuel to run this thing etc. Let me know - thanks!

[marsrace2]

like I said sounds just like the loose plug wire at the coil, you will want to fix this problem either way before tearing it apart to do any mods.

[raptorobbie]

I tore into the bike yesterday to fix the problem discussed.

It was 39 degrees yesterday here and the bike wouldnt start;
1. Checked for spark and had what appeared to be good spark.
2. Plug appeared wet from fuel but still no fire - shot a little starter fluid in and it fired just until the fluid burnt off.
3. Tried the ground wire from coil bolt to engine case - still no fire.
4. Went to parts store to get a couple new plugs.... at the counter, the plug I got was a cross to the oem plug but it was different. The new plug has a much shorter electrode than the stock oem plug that came in the bike. I assume this makes a differnce b/c it changes where the spark is inside the cylinder - guy at the counter had no clue... I took the plug anyhow just to try a new plug.
5. New plug installed - no fire.
6. Removed air screw and blew cleaner into screw hole and watched black stuff come out front of carb - nice! - still no start.
7. Pissed - used starting fluid in carb and bike fired up immediately.
8. Let it warm up, and it seemed to run fine again!

Couple of questions still...

With the air cleaner removed, a constant mist of gas seems to come out at idle, is that normal???

What about the plug - I have the right one coming today.

What size uni filter do I need for a 24mm pwk??

[Nichols Atvs]

Spark plug NGK B8HS or Br8HS either is fine.

Yes a mist of gas is present at idle

Uni filter is a #4200 and outerware is #20-1094

When cleaning the carb take the hole thing off and remove all jets and squirt all orfices until they run clean. Clean jets them self. Spark plugs can be a first place to look when runing bad always keep a couple on hand thats just a 2 stroke thing. Good luck .

[raptorobbie]

"Spark plug NGK B8HS or Br8HS either is fine"

I know what youre saying, but the oem plug is a BR8HSA which has a longer tip or electrode - meaning where the spark is created, is much deeper in the cylinder - I would just assume that makes a big difference - maybe (probably) I'm wrong
:confused:

I was told the BR8HSA does not cross to a BR8HS, but it does cross to an Autolite plug that looks exactly like the BR8HS!!!

thanks for the other info!


rob

[Nichols Atvs]

Been running these plugs for a long time in alot of quads. Hey run what works for you , your paying the bills .Good luck

[SMS]

Go with raptor robbie use b8hs and if it still lookd wet use b7hs it is a hotter plug.