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Discussion Starter · #1 ·
I had problems starting my 660 Raptor when cold so I adjusted my intake and exhaust valves. Now the raptor starts up right away! The new problem that has occurred is that under acceleration, the quad now backfires and shoots flames... I'm not sure what size jets are in the carb because I am the 3rd owner and it has been jetted previously (so they claim). It has a White Brothers exhaust with the baffle removed, and an aftermarket air filter. I was told that it has the stage 2 dynojet kit installed.

My question is, do I need to adjust the fuel screw? Could the exhaust valves need re-adjusted? Any advice or tips to help me out would be greatly appreciated :)


Thanks in advance!
 

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If the problem occurred after adjusting the valves I would definitely start there. Have you took it for a ride since the new valve adjustment if so have you lost any power?
 

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Discussion Starter · #3 ·
It's fixed :) Had to re-adjust the exhaust valves. The exhaust valves were not adjusted properly and were stuck open thus causing the problem...
 

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It's fixed :) Had to re-adjust the exhaust valves. The exhaust valves were not adjusted properly and were stuck open thus causing the problem...
For a valve that was stuck open, it started very good...............:D
 

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Discussion Starter · #5 ·
So today it started shooting flames again, grrr!!! I'll check the valves again tomorrow but I don't see any reason that they should be out of spec....
 

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Master of the Electron
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put 155L/160R Mikuni mains in it.
 

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I had problems starting my 660 Raptor when cold so I adjusted my intake and exhaust valves. Now the raptor starts up right away! The new problem that has occurred is that under acceleration, the quad now backfires and shoots flames... I'm not sure what size jets are in the carb because I am the 3rd owner and it has been jetted previously (so they claim). It has a White Brothers exhaust with the baffle removed, and an aftermarket air filter. I was told that it has the stage 2 dynojet kit installed.

My question is, do I need to adjust the fuel screw? Could the exhaust valves need re-adjusted? Any advice or tips to help me out would be greatly appreciated :)

http://www.youtube.com/watch?v=rZ7rNV0y7s4

Thanks in advance!

A list of your mods and your present jetting may help us determine your problem............
 

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Discussion Starter · #8 ·
put 155L/160R Mikuni mains in it.
A list of your mods and your present jetting may help us determine your problem............
Wish I knew what jets were in it.... The quad was jetted by a previous owner and I was never provided with the correct jet sizes. I'm thinking of buying new jets and starting over just so I know whats going on with it. Before the valves were adjusted it didn't shoot flames at all but was damn near impossible to start. I'm surprised my starter still works after all the abuse I put it through...

I'm thinking its still something to do with the valves because before they were adjusted the quad didn't shoot flames under acceleration. The exhaust valves were set at .176 clearance. My .203 feeler wouldn't go in, and my .15X slid in with no problem. I'm gonna open it up again and re-check the clearance to see if anything changed.

I hope I solve this problem soon, just bought a bunch of goodies I wanna install :) Thanks for the input everyone!
 

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Wish I knew what jets were in it.... The quad was jetted by a previous owner and I was never provided with the correct jet sizes. I'm thinking of buying new jets and starting over just so I know whats going on with it. Before the valves were adjusted it didn't shoot flames at all but was damn near impossible to start. I'm surprised my starter still works after all the abuse I put it through...

I'm thinking its still something to do with the valves because before they were adjusted the quad didn't shoot flames under acceleration. The exhaust valves were set at .176 clearance. My .203 feeler wouldn't go in, and my .15X slid in with no problem. I'm gonna open it up again and re-check the clearance to see if anything changed.

I hope I solve this problem soon, just bought a bunch of goodies I wanna install :) Thanks for the input everyone!
Only one way to find out what jet's are in the carbs...:). I don't remember the stock valve clearence's, it's been a while since Ive adjusted them with stock parts..
Good luck..
 

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Discussion Starter · #10 ·
If the jets were the problem then this should have been happening prior to the valve adjustment, am I right? Is the fuel screw a possible fix? The valves are in spec, and a new spark plug has been installed. I'm really trying to avoid dropping this off at the shop because I'm mechanically inclined, just losing patience haha...
 

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Wish I knew what jets were in it.... The quad was jetted by a previous owner and I was never provided with the correct jet sizes. I'm thinking of buying new jets and starting over just so I know whats going on with it. Before the valves were adjusted it didn't shoot flames at all but was damn near impossible to start. I'm surprised my starter still works after all the abuse I put it through...

I'm thinking its still something to do with the valves because before they were adjusted the quad didn't shoot flames under acceleration. The exhaust valves were set at .176 clearance. My .203 feeler wouldn't go in, and my .15X slid in with no problem. I'm gonna open it up again and re-check the clearance to see if anything changed.

I hope I solve this problem soon, just bought a bunch of goodies I wanna install :) Thanks for the input everyone!
And you did check the valve lash at the proper TDC....... compression stroke.............not at TDC.......... exhaust stroke........................
 

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Discussion Starter · #12 ·
Are the intake valves and exhaust valves adjusted at the same TDC or are they set separately? Right now the intake and exhaust are set at the same TDC..
 

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Are the intake valves and exhaust valves adjusted at the same TDC or are they set separately? Right now the intake and exhaust are set at the same TDC..
TDC Compression stroke...............both intake and exhaust valves are adusted at the same TDC............
If you adjust the valves at TDC exhaust stroke, they will be loose.............
 

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Discussion Starter · #14 ·
Then yes, I believe both are adjusted at TDC compression stroke. If they were both adjusted at TDC exhaust stroke, then the motor wouldn't fire at all correct?

What gets me is that it starts up perfectly every time now that the valves have been adjusted, its just the backfiring issue now. I'm tempted to play with the fuel screw... I'm checking out the FSM now to study the carb.
 

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Then yes, I believe both are adjusted at TDC compression stroke. If they were both adjusted at TDC exhaust stroke, then the motor wouldn't fire at all correct?

What gets me is that it starts up perfectly every time now that the valves have been adjusted, its just the backfiring issue now. I'm tempted to play with the fuel screw... I'm checking out the FSM now to study the carb.
Yes the engine will run when you have the valves adjusted at the wrong TDC, BUT the valves will be adjusted a bit too loose........
 

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Discussion Starter · #16 ·
Yes the engine will run when you have the valves adjusted at the wrong TDC, BUT the valves will be adjusted a bit too loose........
I know exactly what your talking about now that you said loose, because it almost happened, haha. Valves are set at the TDC on the compression stroke.

When I used the .153mm feeler gauge to check the valves they were somewhat tight, but the .153mm did fit. Maybe I'll try backing them off a hair and see what happens. Heading back to the garage to try it out and then I'll update. If it doesn't make a difference I'm smoking a blunt, haha
 

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I know exactly what your talking about now that you said loose, because it almost happened, haha. Valves are set at the TDC on the compression stroke.

When I used the .153mm feeler gauge to check the valves they were somewhat tight, but the .153mm did fit. Maybe I'll try backing them off a hair and see what happens. Heading back to the garage to try it out and then I'll update. If it doesn't make a difference I'm smoking a blunt, haha
How did you check for proper TDC..............
 

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Discussion Starter · #18 ·
How did you check for proper TDC..............
Just got back... I aligned the l mark with the mark on the case and I used a long screwdriver in the spark plug hole to verify that it was TDC. I just checked the intake and exhaust valves and they are exactly right. If I give it some gas very slowly it will rev up normally to redline and seems ok. When I blip the throttle I get the backfires.

If it's a jetting issue then why would this just now start happening? Before the valves were adjusted everything was great except for being a pain to start.
 

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Just got back... I aligned the l mark with the mark on the case and I used a long screwdriver in the spark plug hole to verify that it was TDC. I just checked the intake and exhaust valves and they are exactly right. If I give it some gas very slowly it will rev up normally to redline and seems ok. When I blip the throttle I get the backfires.

If it's a jetting issue then why would this just now start happening? Before the valves were adjusted everything was great except for being a pain to start.
The procedure you used, verifies you have TDC, but not that you are at TDC compression stroke, and this is important when setting the valves................
 

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Discussion Starter · #20 ·


I'm gonna stick my finger in the hole and make sure that its on the compression stroke which I believe 100% that it is already. If I am, I'm gonna turn these 2 screws and see what happens....

I thought that if the backfires happen under acceleration, then the motor was running lean, and if it happens under deceleration, then it is running rich. My local shop is telling me the complete opposite and that if its happening under acceleration then its rich... Who's right?
 
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