murray1886
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Any suggestions for carb settings on a 1995 xp with a 720, wsm head (180psi), and aftermarket flame arrestors? Should I be running cooler plugs also? Thanks
1995 xp 720 tuning
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That is a whole lot of compression. I would run 93. BR8ES but gap them thin at like 20-21. I would open your HS needles 1/2 on the mag side and 3/4-7/8 on the rear. Look at your plugs after a 10 sec wide open throttle run and make sure they are not white or grey. Make sure your not falling off(loosing rpms) at wot. If so then open the highs a little more in 1/8 increments.
murray1886
New Member
I set the carbs up two seasons ago and just never got the thing going.
I wanna say I jetted it 140 hs and 72.5 ls. I dropped the pop off also. Does this rejetting change your suggestions?
murray1886
New Member
bump........
That is quite a bit more fuel. You went up 5 on the low jet and lowered pop off for the flame arrestors as you should have. You went up 5 on the high jets also though. If your still running the stock pipe you will probably have to close your HS all the way. Stock low setting is 1 3/4 turns so I would start 1 1/4-1 1/2 turns with what you have done.
You should get a nice even idle with snappy throttle response on the trailer. Set your trailer idle at 2800 and it should be just right in the water.
You should get a nice even idle with snappy throttle response on the trailer. Set your trailer idle at 2800 and it should be just right in the water.
murray1886
New Member
thank you. I'll give it a shot, do some plug chops and see where we re at. hopefully ill be back with good news 
I think you might be rich even with the HS closed. Remember you want great acceleration. That's what that blue head is for and higher compression will wear those bearings out sooner. Good Luck
murray1886
New Member
I didn't put any of this on... I would have left it stock. The previous owner sold it to me with the trailer for $500 because he couldn't make it run... interesting enough, rear bearing was ate and destroyed the seal. I can't believe the engine didn't cook.
He had these vortex arrestors on with stock jetting and no chock... thought it would be abit lean.
He had these vortex arrestors on with stock jetting and no chock... thought it would be abit lean.
Yes it would have been. I will trade you a clean 717 head plus a little cash if you ever want to trade. I love aftermarket parts. Anyway I think you are ready for testing. It may be a little rich with the 140's and the stock pipe but black plugs will confirm that.
murray1886
New Member
Maybe I was wrong with the HS jets I put in... Im out about 1 and 1/8 on the highs... about 1 on the lows and the thing is running like a beast compered to before.
Plugs are nice and tan... only prob is it really doesn't want to start without giving some throttle and then it takes a sec to level out... I messed with everything and can't seem to solve it... also has a slight hesitation on take off.
You think maybe the pop off is too low and its loading up??
maybe hesitation is the wrong word... more like it winds-up for about half a second
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murray1886
New Member
bump........
That description sounds like cavitation. If it revs up during acceleration without moving forward from the revs you getting(like a clutch in a car slipping).
Pop off needs to be checked because it sounds like your needles and seats may be leaking hence your hard starts. Originally the pop off on that was super high at like 50. With your larger ls jets and those flame arresrors you should still have a pop off of at least 25 and preferably 32ish.
During your hesitation of the line try pulling the choke(or a pump of the primer) and see if that helps. If it is rich then it will just peter out in a groggy way. If it is lean then cutting the air back(choke) or adding a squirt of fuel will make it jump correctly.
Pop off needs to be checked because it sounds like your needles and seats may be leaking hence your hard starts. Originally the pop off on that was super high at like 50. With your larger ls jets and those flame arresrors you should still have a pop off of at least 25 and preferably 32ish.
During your hesitation of the line try pulling the choke(or a pump of the primer) and see if that helps. If it is rich then it will just peter out in a groggy way. If it is lean then cutting the air back(choke) or adding a squirt of fuel will make it jump correctly.
murray1886
New Member
its not cavitaion... the engine just has a half second bog before it kicks in... I'm taking it out in a sec to play with it.
the popoff is at 28 with 1.5 needle if I remember right. I'm thinking its loading up... I may try using the primer as you suggested, if it seems rich ill take the flame arrestor off and see if I can see any fuel dribbling when at idle
murray1886
New Member
its dumping fuel... after a five minute idle, the plugs are dripping.
At this point I only have the LS out 1... and its a pain to start without giving it some throttle.
I think the popoff is too low and when the engine is running maybe the vibration is causing a leak.
I also think I said it was a 1.5 needle... I'm now thinking its a 2 with the 95 gram spring.... any thoughts?
At this point I only have the LS out 1... and its a pain to start without giving it some throttle.
I think the popoff is too low and when the engine is running maybe the vibration is causing a leak.
I also think I said it was a 1.5 needle... I'm now thinking its a 2 with the 95 gram spring.... any thoughts?
murray1886
New Member
bump......
Sounds like your on the right track. What is the pop off? How much pressure does it hold? If pop off is not too low then you will have to go back to smaller ls jets.
murray1886
New Member
not sure why it bothers you.... just bumping it to get different opinions.... unless I misunderstood how a bump works... doesn't it place the thread closer to the top again so people who may not have seen it the first time around may see it the second....?? If not, sorry.... I'm new and may not know the etiquette.
murray1886
New Member
28 psi for the pop off.... you think I can just change the spring and rise the pop off or do you think that will mess up my wot... which seems to be perfect.
Yes get that pop off up into the 30's or even low 40's and it will clean up the low end if you were rich.
murray1886
New Member
I'm going to take a little break off this one since the boat just popped the lower, but I wanted to thank you for all your help Matt, sure is nice to have someone to bounce ideas off of and get some direction, I'll let you know when I get it going right
Crofoot50
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I am on several forums and rarely on this forum do I see any member bump his thread. Matt is doing a great job helping you. Good Luck
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