Going to need help setting up 780 srx

staggs65 said:
Yes that is very likely. It's been a while and I don't have our original messages anymore. I would get out where you can do some pulls and check plugs and wash good.
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Will do. Just need parts to come in and then snow. I'll let you guys know how it turns out. Thanks
 
Ok. Got it running. I went through a couple heat cycles trying to get the richness out from holding the oil cable open. I started with 47.5 pilots, 1 3/4 turns on fuel screw, needles at 3.5, and mains at 156.3 (Partzilla has been terrible this year so I didn't have my 157.5). I am a little sketchy on exactly what I am looking for when checking the pilots. After idling for a few minutes it gains rpm pretty good when I hit it and doesn't cough through carbs or exhaust. The plugs and the pistons are a little wet. Should I go down to the 45 or leave it.
 
I reread the earlier posts and mrviper said I should be fine with the 45 pilots so I changed them. Definitely made a difference. I had to turn the idle up a bit with the 47.5s from where it was when it was a 700. When I went to the 45s I had to turn it back down and the plugs and pistons are a little wet but not much. Must have had too much fuel with the 47.5s and that's why I had to turn the idle up. Does that sound right?
 
drew24 said:
I reread the earlier posts and mrviper said I should be fine with the 45 pilots so I changed them. Definitely made a difference. I had to turn the idle up a bit with the 47.5s from where it was when it was a 700. When I went to the 45s I had to turn it back down and the plugs and pistons are a little wet but not much. Must have had too much fuel with the 47.5s and that's why I had to turn the idle up. Does that sound right?
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yes, your on the right track. with 45's fuel screws out at 1.75 out, and needles raised up it will be plenty rich enough in low-midrange. the mains will be fine as long as the airbox is stock with center shelf in. Now go out and do some short burst of wide open and start to see what color the plugs look like and see where your rpm is, start off short and work your way up to a good 1000ft run.
 
mrviper700 said:
yes, your on the right track. with 45's fuel screws out at 1.75 out, and needles raised up it will be plenty rich enough in low-midrange. the mains will be fine as long as the airbox is stock with center shelf in. Now go out and do some short burst of wide open and start to see what color the plugs look like and see where your rpm is, start off short and work your way up to a good 1000ft run.
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Awesome. That's what I like to hear. If the weather cooperates I will get out and do some runs today and report back. Thanks for the info.
 
IMG_20161217_152040315.jpg
These are my plugs after about 800-900 foot run wide open then shut off and coasted to a stop. New plugs. Rpms started at 8100 and went to 8400 and felt like it was still climbing. Left to right pto,center,mag Also compression was mag 160, center 170, pto 160. With the same tester that read 120ish when it was a 700. I just noticed can't really see much on these plugs from the pic but it was starting to turn brownish on the porcelain. I should be able to get some more runs tomorrow. temp was about 25 degrees f.
 
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The 170 reading is a bit odd. I had 150 across the board on that motor with my tester. Testers will read differently but the 1 higher is strange

Not much to see on the plugs yet.
Were they wet?
 
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staggs65 said:
The 170 reading is a bit odd. I had 150 across the board on that motor with my tester. Testers will read differently but the 1 higher is strange

Not much to see on the plugs yet.
Were they wet?
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I will do another compression test today. That was with the motor cold. I will check with it warm too and see what that says. The plugs were wet. I ran the sled a bit yesterday and so far no problems. It got pretty cold. Not sure if it helps but these plugs are after about 65 miles and it went from about 15 degrees f to -4 when I pulled it in. I didn't hold it open but for short bursts when it got cold just to be kinda safe. The pto has seemed a little richer than the rest throughout all testing so far. That seal for the powervalve on that cylinder is messed up so not sure if that is the reason or not. It ran good and at 10-15 degrees F the clutching was spot on 8200 going up to 8500. Left to right pto,center,mag. 93 octane with half bottle of klotz octane boost. Definitely felt a power difference from the first day when it was 25 degrees and yesterday at about 15. IMG_20161218_210530675[1].jpg
 
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I think youll find it much easier to read the spark plugs if you run a set of used ones, when they are new it takes a while to "color" them and read the signs left.
 
I haven't done any more testing lately but I did check the compression again cold and it was 172/180/172. This was after it had the 65 miles on it. So I decided to try to check the squish. The only solder I had was .030 so I twisted it tightly then checked. Seemed to work good but I will get better solder and try again. Results are pto-.038, center-.027, mag-.038. I did it several times and came out the same each time. That was on one side of the piston above the wristpin. Not sure if you are supposed to do both sides at the same time. Seems tight to me. Any thoughts?
 
ya, that's tight for a trail engine, need something around .055". Your reading can be off with what base gasket used? some aftermarket paper ones are thinner then the stock Yamaha steel one. It also can be off with how tight you squeeze the calipers on the solder, but no matter that's a little tight on a trail engine. It would also explain why you have higher then normal compression readings.
 
mrviper700 said:
ya, that's tight for a trail engine, need something around .055". Your reading can be off with what base gasket used? some aftermarket paper ones are thinner then the stock Yamaha steel one. It also can be off with how tight you squeeze the calipers on the solder, but no matter that's a little tight on a trail engine. It would also explain why you have higher then normal compression readings.
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Sorry, forgot to add its a stock Yamaha steel gasket. I was trying to be gentle when measuring. Should I consider adding another base gasket or does that change things too much? And if I do could I use a used one I have here that I took off when I changed top ends? Its also stock Yamaha and it looks good yet. I really don't want to burn her down.lol Thanks.
 
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even adding 1 extra base gasket is only gonna raise it another .010-.011", your center reading of .027" would still be too tight at .037-.038". The bad about stacking up base gaskets is you will gain deck clearance and you cant get rid of that, it might make the squish clearance better but you lose the ability for the head to work properly because you moved the whole cylinder up, then your piston at BDC can end up not in time with the transfer port openings and main exhaust.

I would recheck it again with thicker solder, I use .060-.080". if it comes out to the same reading, the only way to correctly fix that is to have the heads rechambered, and the center one would need to be set up for that cylinder if its that much different again on the reading.

did you pay attention to the deck clearance when you put it together? the pistons should of just barely sat down in the cylinder on the edge, about .010", if they are flush or above then the cylinders have been machined on the bottoms.
 
I will go get some better solder and recheck. I didn't pay much attention to the deck clearance but I remember thinking they looked awful close to flush with the top. I can pull a head off after I recheck squish and check it out. I am not sure but I am thinking this motor might have had a burn down at some point in its life. Two of the cylinders are stamped on the backside with 0830 and 0831 and the one I have in the middle is different. I cant see it to tell exactly but it was 1134 or something close to that. Maybe that cylinder was made to try to match the others. Not sure but a theory to why it has more compression. Is there a chance this was made to have two base gaskets? Seems like I read that some were made to have 2.
Where I ride I don't have any problems getting fresh 93 from the bigger stations if that helps.
 
Ok. Got the heads off. Looks like the pistons are maybe flush or a bit lower until you rock them a bit then they go above. It looks like they were hitting the heads. Especially the center one and I am guessing that is why it looks like it was going past the o ring. IMG_20161221_123413732[1].jpgIMG_20161221_123420522[1].jpgIMG_20161221_123432969[1].jpg
 
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