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I am looking to buy the low compression domes for my 05 800 mod motor so I can run it on pump gas. Do any aftermarket places sell these or do I just order them from Doo? Are the domes all I will need or do I need a different head as well? I will use it mostly for ditch riding and playing, not much long trail riding. Any other info on parts/changes I will need and a starting point for jetting would be appreciated. I did a search but couldn't find what I was looking for.

Thanks,
Josh
 

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joshz79 said:
I am looking to buy the low compression domes for my 05 800 mod motor so I can run it on pump gas. Do any aftermarket places sell these or do I just order them from Doo? Are the domes all I will need or do I need a different head as well? I will use it mostly for ditch riding and playing, not much long trail riding. Any other info on parts/changes I will need and a starting point for jetting would be appreciated. I did a search but couldn't find what I was looking for.

Thanks,
Josh
[snapback]739179[/snapback]​
Call bill cudney he may have something laying around, I was able to get a good deal on one of his heads that was used for my 04' mod. You do not need the whole head though you can just get the domes or have yours recut. Ok here are some setup tips I had to deal with the samething earlier this year. If you are running the twin pipes you want to be clutched around 8400-8600rpm or you will not make as much power, twin pipes make max power at higher rpms, if you are running a single pipe use 8000 rpm. You will have to reclutch after the conversion to pump gas you may have to take out pin weight or change the primary spring to get those rpms up."Had to change the spring on mine, get a spring with a higher finish force". You dont have to do that much as far as jetting put in 340 or 350 mains, move the needle clip to the second position from the bottom. I use the stock pilots and my airscrews are 1/2 turns out. Hope this helps...

later,
kep
 

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kep said:
joshz79 said:
I am looking to buy the low compression domes for my 05 800 mod motor so I can run it on pump gas. Do any aftermarket places sell these or do I just order them from Doo? Are the domes all I will need or do I need a different head as well? I will use it mostly for ditch riding and playing, not much long trail riding. Any other info on parts/changes I will need and a starting point for jetting would be appreciated. I did a search but couldn't find what I was looking for.

Thanks,
Josh
[snapback]739179[/snapback]​
Call bill cudney he may have something laying around, I was able to get a good deal on one of his heads that was used for my 04' mod. You do not need the whole head though you can just get the domes or have yours recut. Ok here are some setup tips I had to deal with the samething earlier this year. If you are running the twin pipes you want to be clutched around 8400-8600rpm or you will not make as much power, twin pipes make max power at higher rpms, if you are running a single pipe use 8000 rpm. You will have to reclutch after the conversion to pump gas you may have to take out pin weight or change the primary spring to get those rpms up."Had to change the spring on mine, get a spring with a higher finish force". You dont have to do that much as far as jetting put in 340 or 350 mains, move the needle clip to the second position from the bottom. I use the stock pilots and my airscrews are 1/2 turns out. Hope this helps...

later,
kep
[snapback]739481[/snapback]​
Hey kep
Did u have much trouble clutching w/ twins- i've got an 02 800 that i just put twins on- not mods but similar rpms- and can't get the revs no matter what weight i put in the adj. pins. I run a dynamo joe clutch kit with a 230/360 primary- was thinkin the same as u just change finish force- maybe go to a 230/410. What do u think
 

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That is the same problem I was having, dropped the pin weight down to 16.5 grams from 18 grams and could only get 8000-8100rpm on the tach on clicker #6. I had to buy a new spring went to a 280-460 spring from a stock 250-380 "which I have yet been able to test, I am probably going to have to add weight now". If your sled is not a mod I dont know if you will ever be able to get those rpm's without getting your mpem reprogramed, because I have heard the trail sleds have a revlimiter programed into their mpem.

later
 

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kep said:
That is the same problem I was having, dropped the pin weight down to 16.5 grams from 18 grams and could only get 8000-8100rpm on the tach on clicker #6. I had to buy a new spring went to a 280-460 spring from a stock 250-380 "which I have yet been able to test, I am probably going to have to add weight now". If your sled is not a mod I dont know if you will ever be able to get those rpm's without getting your mpem reprogramed, because I have heard the trail sleds have a revlimiter programed into their mpem.

later
[snapback]739836[/snapback]​
Hey kep
Thanx for the info I think i will try a 230/410 and 230/390 and see what happens- and i did have the mpem recurved to work with pipes
 

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Like I mention to you, you may have to start to jet down and try to get some heat in the pipes to turn them on.

Hot pipes make "great peak hp" however for a cost of a loss of torque in lower rpms. Heated pipes will turn on at their rated peak rpms.

Cool pipes make "great peak torque" however for a cost of a loss of peak rpm hp.
Cooler pipes will turn on at lower rpms than their rated peak rpms.
 

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Dynamo^Joe said:
Like I mention to you, you may have to start to jet down and try to get some heat in the pipes to turn them on.

Hot pipes make "great peak hp" however for a cost of a loss of torque in lower rpms. Heated pipes will turn on at their rated peak rpms.

Cool pipes make "great peak torque" however for a cost of a loss of peak rpm hp.
Cooler pipes will turn on at lower rpms than their rated peak rpms.
[snapback]741174[/snapback]​
Hey joe I think the jetting is quite close on my set-up-hard to tell though wash is very vague- talked to kelsey at rkt and he said w/ stock pistons they are always overheated so i should see no wash- plugs look alright- im used to being able to use wash- at best im only 1-2 sizes rich depending on the day do u think that would make the difference- another question did u send some of your kits out w/ the 230/390 spring????
 

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Josh...you can get in touch with Jason at Straight Line Performance as well...i had him do up a set of inserts for my mod so i could run premium pumpgas...theyve worked out great for me.
 

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Kep Did u get any testing done w/ new spring. I switched from 230/360 to 230/410 but we got about 2 ft. of fresh snow so it is hard to tell how it works. It feels better not quite as doggy but i don't know what r's it will pull on hard pack. Too much snow right now might have to put in a diff 2ndary spring foe all the snow we got now.
 

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02z800 said:
Kep Did u get any testing done w/ new spring. I switched from 230/360 to 230/410 but we got about 2 ft. of fresh snow so it is hard to tell how it works. It feels better not quite as doggy but i don't know what r's it will pull on hard pack. Too much snow right now might have to put in a diff 2ndary spring foe all the snow we got now.
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I did get a chance to ride sunday although the conditions got really bad toward the end of the day, with very little snow and high temps. The spring I put in was a 280-460 it did get the rpms up "straight to 9000rpms on cliker #6 had to go to #5 to be acceptable" but its is not tuned perfectly yet, I needed to add weight but not enough time to do that and ride. I was planning to do that the second day of our ride along with dropping the main jets but by the time we got back from riding sunday there was no point in staying a second day the trails were done. I did add weight when I got home "went up to 18g" but think my riding may be done for the year. The sled ran good I just felt it lost some pull so I think that adding the extra weight will bring it back. I definitly have room for tuning with this spring, I could probably add even more weight maybe 19 or 20g's, it was really hard to get a read by the end of the day the sled was really rich 950 degrees on the egts bogging down on the topend but still pulling 8400rpms.

later,
kep
 

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I had the mod motor w/ twins and the power was good but gas mileage sucked. I had the motor ported, switched to a single pipe, and got an EGT to lean it out. My gas mileage is every bit as good as the new Doo motors and I still have the mod carbs on it. Power is great too!

As for a head, you can use any 800 pump gas head. Mine is from a 2002 800 summit that was modified to the newer HO specs.
 
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