Jay1823
New member
I have a 93 Exciter 570 engine in my dune buggy, i just replaced the 440 i had in it since i was hungry for more power and wanted something water cooled. The engine has a set of twin PSI pipes running a 310 main jet. Here's my problem, running it down my street it'll only rev so high and doesn't want to go any higher. But when i take it back home, throw the rear end in the air so it's not under load it'll wind out all the way. Do i need a bigger main jet, is it fuel starved? Plugs look great, nice tan color. Any insight would be greatly appreciated, i'm supposed to take this out next week with friends and i'd hate to miss it. Thanks
Would look at clutching before leaning it out.......... need that load factor.........
YamiSmurf
New member
clutching or gearing????
Jay1823
New member
Well i've been jetting it down slowly and taking it out for quick runs. Today i ran it with 260's in it and it ran considerably better, pulled the plugs and they looked good but it's still not hitting maximum revs. Do 260's sound even correct given mid 70 temperatures with twin psi pipes. I have a set of 250's i'm gonna try tomorrow and see how it goes. I'll post some pics of all my gearing changes and see what you think. Granted the gearing was almost the same when i had the 440 in it and it ran real good with the 440
Jay1823
New member
So here's how the gearing, stock 570 drive clutch to what i think is 440 driven clutch and chaincase. Down to the jackshaft where i have i believe a 14 tooth sprocket up to the large sprocket. I haven't measured anything out but i could if it would help someone.
That's the non SX 570 motor which was around 88 HP if I recall. What 440 did you have in it before?
Jay1823
New member
If memory serves it was an early 80's 440, i think it was supposed to have around 50 hp. When the 440 was in the buggy the chaincase was the same, the small sprocket is the same size but the large sprocket was a bit smaller. As for the gearing now i was gonna measure everything out but i thought this would be easier. I used a paint marker and marked the driven and than i marked the large sprocket. For every rotation of the driven the large sprocket rotates 7/8 of a turn.
By the way how can you tell what 570 it is, i thought they all were around 100 hp. just trying to learn as much as i can, i'm just not used to carbs, i'm used to tuning on a laptop, i like data logging and reading graphs, makes more sense in my head
By the way how can you tell what 570 it is, i thought they all were around 100 hp. just trying to learn as much as i can, i'm just not used to carbs, i'm used to tuning on a laptop, i like data logging and reading graphs, makes more sense in my head
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The 93 SX motor (only year it was made) had flatslide carbs, not the round slide ones you have in your picture. There are some other differences but I can't remember them anymore. 
Did you have a close look at that drive clutch to make sure nothing is sticking/binding? Did you adjust the clutch offset for the 570?
Here's a link for the OEM settings for various years of yamaha, main size, offset etc.
http://www.totallyamaha.com/snowmobiles/AAATuning Chart/Specs.htm
Did you have a close look at that drive clutch to make sure nothing is sticking/binding? Did you adjust the clutch offset for the 570?
Here's a link for the OEM settings for various years of yamaha, main size, offset etc.
http://www.totallyamaha.com/snowmobiles/AAATuning Chart/Specs.htm