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Discussion Starter #1 (Edited)
Hey all, broke my 2nd decompression pin on my fresh 720 build with stg 3 hotcam, wondering if this is common? can i not use the stock decomp assy? went down like this finished timing new cam, rotated a few times to ensure everything was good, put cyl head cover on, set valves rotated to check. Binding on decomp pin (discovered later) after i broke the pin in half with a lil to much force, freed up & seemed fine, tore down found decomp pin sheared. installed new pin now it's binding again. please help...
 

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Hey all, broke my 2nd decompression pin on my fresh 720 build with stg 3 hotcam, wondering if this is common? can i not use the stock decomp assy? went down like this finished timing new cam, rotated a few times to ensure everything was good, put cyl head cover on, set valves rotated to check. Binding on decomp pin (discovered later) after i broke the pin in half with a lil to much force, freed up & seemed fine, tore down found decomp pin sheared. installed new pin now it's binding again. please help...

Never heard of that problem before..............
I do not use the decomp mechanism, I plugged all holes to keep oil pressure that the decomp mechanism filled..............
 

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Discussion Starter #3
Cool, thanks, that`s what i wanted to hear, so how did you plug all holes.... (sorry my question mark isn`t working) what all did you remove... total assy... all hardware off cam sprocket.... the whole works.... or can i not install the pin but install the rest, and not have to plug any holes... thanks BD
 

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You can fill it by welding them shut. Thats what most people do. It sounds to me that you have the end pin (with the flat spot) in wrong or 180 out. I would check that. You should be able to move the gears to the outer edge fo the gear and the pin should be flush with the lobe.
 

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Cool, thanks, that`s what i wanted to hear, so how did you plug all holes.... (sorry my question mark isn`t working) what all did you remove... total assy... all hardware off cam sprocket.... the whole works.... or can i not install the pin but install the rest, and not have to plug any holes... thanks BD
I used small frost plugs to close the three holes occupied by the decomp mechanism...........
I did not like the welding approach method for the reason it is a permanent method and I felt that maybe the cam may distort from heat.......
 

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Discussion Starter #6
Ok thanks much guys, what should i do with all the hardware hanging off the gear...
remove all... that wouldn`t throw anyting out of wack to remove those spring accuated arms, etc.....
 

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i had the same problem,except my motor blew apart, i flarred the ends on the back and tack welded them so they wont move
 

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I just tach welded the decompression shaft in the cam. 4 small tacks on the end of the cam. That way if I wanted to remove it I could cut the welds with a dremel and smooth the end of the cam up with a belt sander.

Then just strip all the stuff of the cam sprocket
 

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Ok thanks much guys, what should i do with all the hardware hanging off the gear...
remove all... that wouldn`t throw anyting out of wack to remove those spring accuated arms, etc.....
All that mechanism on the gear can be removed,,,,,,,,
 

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Let us know how it starts when you've finished removing the De-Comp...........

Just Curious......... :)
 

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I'm also curious to "Why" the de-comp pin is shearing off. Can you post pics of the pin or pieces of the pin. Can you post some pics of the rocker arm foot the pin operates off of??
 

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Discussion Starter #12 (Edited)
Sorry guys i made a mistake in my first msg, i sheared 1 pin, stopped b4 i sheared the second, here`s some pics of the pin & actuator, seems to work fine out of the machine, kinda feels like it might be hanging up in the pin hole a bit. gonna get rid of it either way, can`t be having this gonna race on the 29th, and seat time on the wife`s 400ex just isn`t cutting it.
 

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I've never seen a pin break like that so before removing the decompression-ability of the motor I would inspect the cam and look at the assembly of the decompression more closely. That said, I'd like to comment on the utility of removing the decompression. I don't mean any disrespect toward all you guys that run without the decompression, but that set up does not apply to all types of racing/riding. I came up with my own mod to convert the cam over to no decompression and still maintain the oil pressure through the top end and cam.
I was running a stage 2 cam 719 and did everything everyone suggested on this site. I made new heavy duty battery cables and bought the Grizzly battery that barely fits in the battery box backwards. I still had problems starting the motor and wouldn't trust that set up 15 miles from my truck on a long woods run. It was hard on the solenoid and starter motor both. I re-installed the compression release with stronger Chromoly Rhino 660 Camshaft Pins from Weller Racing -(it's the stock pins on the front of the cam that can brake off and toast a motor according to the desert racers).
http://www.wellerracing.com/
If you want to try no decompression and be able to switch back to factory decompression without the hassle of welding up the cam then maybe my previous post will help. I'm sure for those people who unload their bike and stay within a couple of miles of their truck and don't have to cross steep Appalachian mountains getting back when the solenoid or starter goes out then that mod is wonderful, but it wasn't for me. Good luck.

http://www.raptorforum.com/forums/showthread.php?t=63553
 

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I have used a stage 3 cam, and an X4, I have had as high as 12.5 piston, with shaved head and cylinder, grizzly battery, extra heavy starter wires from battery to solenoid and to the starter, I use no decomp, all holes plugged in the cam, and its starts great, the engine never locks..................
 

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I would guess my bike wasn't starting as well as others on here without the compression release because I run the stage 2 cam which has less overlap, 42 degrees, and the intake valve closes at 49 ABDC. The stage three has 53 degrees overlap and intake closes at 64.5 ABDC.
I'm not saying my bike didn't start but the bike would protest every time I hit the starter and that in itself didn't inspire confidence in the endurance of the set up.
 

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I would guess my bike wasn't starting as well as others on here without the compression release because I run the stage 2 cam which has less overlap, 42 degrees, and the intake valve closes at 49 ABDC. The stage three has 53 degrees overlap and intake closes at 64.5 ABDC.
I'm not saying my bike didn't start but the bike would protest every time I hit the starter and that in itself didn't inspire confidence in the endurance of the set up.
Was this on hot and cold starts or just on cold starts..............
 

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I'm also curious to "Why" the de-comp pin is shearing off. Can you post some pics of the rocker arm foot the pin operates off of??
I'd still like to see the rocker arm foot.

OK again, My motor without any de-comp. It would roll to tdc compression on any stroke and STOP dead in it's tracks. :wow:

MHO is not to remove the de-comp.........
 

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OK again, My motor without any de-comp. It would roll to tdc compression on any stroke and STOP dead in it's tracks. :wow:

MHO is not to remove the de-comp.........
That is what mine would do if it was half way up on the compression stroke. I could bump the starer button a couple times and it would ethre kick back down to bottom dead center or it would force it past the compression stroke.

Once it was at bdc i could hit the start button and it would crank and fire up. I got tired of having to teach people over and over how to start it so I am putting the decompression mechanism back in. I am using Bigdaddy660R's decompression setup. His setup uses pins that have nuts on the back side. So that way they wont walk out.

josh
 

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Discussion Starter #19
Here`s a few pics of the rocker arm feet, both exh, complete rocker arm assemblies have about 100hrs on them, no visible damage from the pin that i can see.
 

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Here`s a few pics of the rocker arm feet, both exh, complete rocker arm assemblies have about 100hrs on them, no visible damage from the pin that i can see.
I'm not seeing any severe damage, shearing that pin off would make. I know if the de-comp is 180* out, the pin face will mushroom & the rocker arm foot will show a gouge in the pad...........
 
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