jetting help

M

marcush

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Dec 24, 2003
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hi guys I have a 97 mm 700. I ported it to race logic specs and I also put a peak head on it with 21cc chambers. Compression is at 128 psi. I also have my carbs bored to 35.5 mm, Boost bottle,reed spacers and carbon fibre reeds.Airbox mod also.I am at 2200 feet. My jetting is at #1 156.3,#2 155,#3 155.Neddles at 2.5, pilot jets 57.5,fuel screws 1.5. Carbs are clean and synchronized.stock pipe with mod done to it.Here is my trouble when I snap the throttle I get a bog.I was runing 52.5 for pilots and increased it to 57.5 and it is still there but not so bad at higher rpm.When she gets over the bog she pulls real hard and works great.Should I go higher in the pilots or do something with my air jets? My belt is sitting about a 1/16" high in the secondary.
 
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air jets

Also can someone explain what affect the air jets has on jetting .Does it affect jetting all the way through to wide open throttle?
 
well guys here is an answer to my own post,my local yamaha shop informed me the air jets only affect the bottom end only.Come on guys there are lots of you out there with ported,bored carbs and boost bottle on a red head 700.I have 62.5 piot jets ordered and .8 air jets.Please give some feed back.am I on the right track with this?
 
Can't answer your ? but if you want to sell the 52.5 pilots, let me know, I'll take them. Maxdlx
 
Your Jetted WAY TOO RICH!!!!!! Your porting is doing almost nothing with the single pipe on it. The peak heads are just slightly tighter then stock with 21 cc domes at 2200 feet. Im guessing your mains should be in the 142 range and pilots 47.5. Its hard to tune a sled over the net but your way out in left field with that set-up. Dont forget the bog could be clutching too. ===SRXSRULE===
 
Sorry guys I miss wrote my jets the mains are #1, 146.3 #2, 145 #3, 145.Also the company I purchased the boost bottle from informed me that a lean bog would be experanced if you also have reed spacers and carbon fibre reeds so he said go to a #50 pilot jet or a 52.5.Yamaha specs are main jet #1, 143.8 #2, 142.5 #3, 142.5 pilot jet #50, needles 2.5,fuel screw 1.5 so as you can see it is not jetted real real rich.It does have bored carbs and air box mod so more air = more fuel.Tomorrow I am trying the fuel screw at 2.5 with needles in # 3 position and #57.5 pilot.If anybody has a similar set up or can help please do help me.Also I don't believe this is not a clutching issue as the bog is there while it is on the stand and it only last the length of a second.
 
There's no way that you need that big pilot. The .8 air jet might pick it up a litle. What you are not telling us is, are you bogging right off idle or where your clutch is engaging?
 
i think your pilots are too small i have 50s on my exciter and 160 mains never changed the air jet and my low end is rippen
i also have the same porting but no reeds of course
but im bored out to almost 600 cc w/ DG single pipe
i would buy the next couple sizes up on those pilots and see if that helps
remember the bog can come from a lean condition too
Richie
 
What's correct? That it bogs right off idle? What's it do on the jack stand? Also, the belt on 97SX's is 1/16 (approx) below the top edge of the secondary..
 
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It bogs on the stand .At idle,at 4000rpm,at 5000rpm it bogs,at 6000rpm no bog on stand or on the snow
 
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the belt is brand new and about 1/32 high,I can understand a belt down in the secondary give you a bog,not so sure of one alittle high I would tend to believe it wouldn't
 
Does it bog with the choke part way on? If it clears up the problem then you have a fuel delivery problem. Did you have the motor out? Is the centerline and offset correct. Bad offset will create a really bad bog. These dimensions are critical. Be sure they are right. I'm leaning towards the carbs being bored too wide and leaving air flowing around the slides. Belt dimensions on 97's are below, not above. You could also have a vacuum leak around the crank seal or around the reed plates or carb boots. Spray some Gumout around these areas and see if the idle picks up. That should tell you something.
 
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The offset and alignment is ok as I have the proper tools for that.The carbs were bored as per hauck specs 2.5 mm over stock.when I did flip the choke on and off it did appear to help to some degree.Maybe I should flip the choke 1/2 on and leave it on then snap the throttle.I don't think there is trouble with the carbs bored to much as you should have problems with idle and I don't
 
crank seal is ok and I will try that around the carbs.I kind of ruled that out as you generally have a crazy idle with a vacuum leak. Rpm would up and down and she is running great at idle
 
i could be wrong but all this work on the intake and nothing to the exhaust? an engine is like a pump...sucks air in and blows it out...the way you have it set exhaust can't get out...put a set of pipes on it!!!
 
pipes are coming man no worries on that I did the low dollar stuff first porting cost $125 boost bottle $50 and carbs bored free for baby sitting someones wife
 
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