78 Exciter Jetting & Reeds

GP396

GP396

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Dec 22, 2006
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MI
What was stock on the 78 Exciter. Seems that a 90 Slow and 145 Main, but when I shop around to buy these the closest I see for the mains are 138, 142, etc. Nothing right on 145. Was the stock set up on the rich side?

I just got some boysen power reeds to put in and one reed is reinforced to make it stiffer. Would that be the top or bottom reed or does this not matter. I just got the engine apart and the stock reeds are the same top and bottom. Also look to be in perfect condition so is there anything to gain with these boysens?

Appreciate any and all feedback.
 
Main 152
Slow jet 90
rpm's 1500
Don't know about the reeds
Main air jet 180
power jet 230
power air jet 250
slow air jet 100
pilot screw 1.5 turns out I believe
starter jet 160
This came out of my manual
 
I don't know anything about the boysen reeds, but I did buy a set of carbon fiber V-force reeds for my 98 SRX and they grenaded in a very short time, hardly any miles at all. Plus, if there was a power improvement, I couldn't tell. I took them out and put the stock Yamaha reeds back in it works tickety boo.

Are these boysen reeds carbon fiber? Wasn't aware they made them for these old girls! G.
 
Not Sure

They are certainly made of some type of composite. Not metal like the yamaha ones.

Ok, now to sound really stupid (I'm just used to my old diaphram carbs), what the heck are all these air jets, power jet, and starter jet (in the choke I'm assuming). When I look at the schematic I can only locate the Main and Slow.

tx
 
GP396 said:
They are certainly made of some type of composite. Not metal like the yamaha ones.

Ok, now to sound really stupid (I'm just used to my old diaphram carbs), what the heck are all these air jets, power jet, and starter jet (in the choke I'm assuming). When I look at the schematic I can only locate the Main and Slow.

tx
Click to expand...
I agree, I don't see all the jets either. Must be there somewhere
 
Reeds

Got the reeds figured out. Pretty self explanatory after you open the package :oops:
 
went up to houghton lake sunday night at the super 8. my slightly modified exciter was running like a banshee, put down my brothers 97 V max in 6 inches of powder on snowbowl road...
 
No sir!

Buck,

This ones all torn down right now. Spent last night cleaning all the gunk out of the belly pan. Going to do a little sanding and touch up to put a stop to a little surface rust on the bulkhead. This is going to be a rider so I'm not going nuts on it.

Just got the jugs back. .020 over and they look good. Looks like he did a little port work on the exhaust sides. Pistons, rings, pins, bearings, gaskets, seals, reeds, etc, all just sitting on the bench waiting for my attention.

Split the case and sent the crank off to be checked. Gentleman that did my jugs said he'd check it for free. Since it was coming out for me to do the seals I'm taking him up on it.

Took the carb apart also and I have a 145 main and a 90 slow. Since the Boyesen reeds can supposedly richen it up on the high end and lean it on the low, I'll go to the 100 slow jet and by a couple smaller size mains to play with after I see how things look.
 
cool, i think i'm not going to install mine yet, its just running too good and i dont want to mess up the jetting. We should get the exciter guys together for a lake race sometime, just for funzees. I go to lake city a lot and lake missaukee gets a hard pack winter highway from the snowmobiles. Well anyway keep me posted on the jetting...
 
I'll keep you posted

Won't be done until after the holidays. Off to Mexico for work next week, then the family starts showing up for Christmas, then a Wedding the following weekend, and probably can throw in a couple days worth of recovery after New Years.

I'll be doing good if I hit mid Jan. Needs to be ready for the second Sat of Feb for the Long Riders Relic Run. It's my backup sled this year.
 
reed

You'll like the reeds, better throttle response after you get them in. I ended up leaning it out a little more one size after I put mine in. I've got a '78 I vintage race. cool sleds. later Mark
 
Good to know

GMan,

How much leaner did you have to go on the Main. It had a 145 in it and I believe that was stock (is for the 79 anyway) and I'll start with that to play it on the safe side.

I heard the reeds will lean it on the low end. I can't seem to find anything but the 90 jet. Would like to take to 100.
 
jets

I think I only dropped one size I'll have to look. I switched to BR8ES plugs too to get a little hotter spark and so far so good.
 
what do your exciters top out at? i swear mine will do 75 all day long, maybe a little over 80 if its fifteen degrees out?
 
I checked and I got a 145 in my Keihin butterfly carb. I've got a slide carb off a 77 I might put on there and check out.
I think mine'll do about 75-80 too. Keep it pinned to the handlebars,,,,
 
I think the 145 was stock.

Never riden mine so can't say how fast.
 
wls said:
For the 78 ex440, stock is #152, main
Click to expand...

Wls,

Is this from a 78 Yam Manual. I know you posted this earlier but I have found nothing that correlates to the 152. On the Yamaha web site in the parts catalog they don't even list a #152 for the 78-81 Exciters.

On a 79 Service Data Sheet it shows #145 as Std. Same for the 1980 & 81

I'm not aware of anything different between the engines that would warrant a #152. Maybe since it was the first year going to that carb they went to the safe side of rich in the manual. The 76 & 77 Keihin slide carbs did have jets up in the #150 range. 78 on was the butterfly.
 
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