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I didn't read both sets but my primaries (smallest of the two) is an 80 whereas stock is 68. I'm not even sure about the highs since I didnt check. The plugs are black and soooty. Should I go down to stock jets? 82 cb750sc Running k&n filter in stock intake box and mac 4 into 1 lord knows what the po had in them I just know it runs ok for now. Let me know what jets to start with please.
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Administrator
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i run the box and a 4x1, 75s and 110s on a 79f do okay
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I have always heard 110s are the go to but wasn't sure of the other. I may try 70 110
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Administrator
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well, 'cause sometimes I feel like there could be more low end power, like it could be starving a bit.
some times more than others.
I've noticed, when this happens, if the choke is pulled maybe half way out the thing takes off,
much more grunt,
like it just needed a bit more richness in mixture.
I have a feeling, 76, 77 on the small ones would do the trick.
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by small you meant slow/pilot correct? since the main itself is actually physically smaller...right?
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I just cheked and I have 68, 108, 35 in all 4. Plugs are very sooty when doing plug chops. Should I change to say a 60? I know if cruising at low rpm's in say 3 or 4th (~3-3500 rpm's) the bike surges. What do y'all suggest? 82 750sc stock box, k&n filter, mac 4 into 1, bench synced, mixture screws at 1.5 out.
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Administrator
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That's pretty weird, the surging thing, maybe a vacuum leak somewhere?
You sure you have the boot clamps tight?
Those jets, you should be lean I would think.
With that jetting, and all 4 black, I dunno.
I wouldn't mess with the jets just yet.
70s, 110, that's just more fuel.
It being all 4, you sure the choke butterflies are opening all the way
when the choke knob is pushed in?
I'd check to see if the needles, that slide into the main jet, some can be raised or lowered,
could be lowered a notch or 2 if possible. You raise the clip, moving the needle deeper into the jet,
letting less fuel pass.
Then the float adjustment, if possible, in the carbs.
Make sure it's not kinda flooding.
I dunno, all 4 black, something is stopping that thing from breathing.
A clogged exhaust pipe baffle, take that sucker out an see how it runs,
same with that airfilter.
Step back and take a break, why is that thing running rich, what's choking the air or flooding it?
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Administrator
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This post was updated on .
Or it might need a good syncing, gauges and all.
Anyone know if syncing would help the surging?
If you're gonna go the jets route, I think there's a kit out there
for about 50 bucks, just jets, gives a good selection to play with.
Good looking bike.
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When ever the bike is warmed up and you get better perfomance with the choke out that means the idle jet, slide needle and maybe the main jet need changing.
IF you have the stock air box and filter and you only have changed to aftermarket exhaust,
you do not need to re jet. Only a mixture screw adustment.
IF you change the exhaust AND the intake system you will need to change the idle jet, the slide needle clip position (or secondary jet) and the main jet.
On a Roadstar Adventure.
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Syncing will not help surging.
Surging can be from float levels being incorrect.
On a Roadstar Adventure.
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On those carbs the secondary jet is like the needle clip position on earlier carbs.
On a Roadstar Adventure.
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No float adjustments and one is obviously higher than the others, kinda strange.
Tried the choke thing and it just makes it bog with the choke out
Carbs are synced.
Needle can't be moved its a solid needle.
I put some marvel oil in the cylinder heads maybe a stuck ring is letting some blow by happen
Exhaust not clogged it's brand spanking new. Not even a full tank of gas burned through it.
The airfilter is the stock replacement k&n and new
I did notice that with the epa hoses (ones from the case to the airbox, when unplugged, you can see smoke coming out)
All mixture screws set at 1 1/2
Choke butterflies open fully
All carbs cleaned thouroughly
Carb boots seem to seal well (what should I do if they dont?)
Hmmm don't think I missed anything. Will not be touching the jets for a while. I hope I don't need new rings.
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Administrator
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A compression test will show bad rings, but it sure looks like you have everything covered.
With all you've done, maybe it is time to play with jetting.
More choke makes it sputter says to me yes, you're running rich.
The Honda dealer may have some, that's where I picked mine up, 5 bucks each.
Let us know what happens, even if it still stumps you after a jetting change.
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will do buddy. im pretty darn thorough %90 of the time but i always ask because maybe i missed something yall would think about lol. im going to do a compression test soon maybe this weekend.. or hopefully tonight. if compression turns out good then ill be heading to jetsrus.com to order some smaller jets.
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Administrator
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I was thinking about your bike, you mentioned the floats, one looking different.
Wonder what's up with that.
Lucky mentioned float level can cause some of the stuff you mention.
There was a guy on here a while back, had his in upside down.
I think there's a way to check float level while running, a piece of real small
clear tubing tapped into the drain on the carb bowl, wrap it up and around
kinda past the top of the carb.
Let the carbs fill, the fuel should fill the tube just as high as the level
in the float bowl. Check that measurement against the manual.
Maybe get a pic of the float that's supposed to be in that carb off the net,
who knows, someone might have changed something before you had it.
I had 4 different pilot jets in the ones on my bike when I first tore 'em dwn
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no its the identical float it just sits a little higher up than all the others....they are plastic so not adjustable.. thats what confuses me. now i have developed this weird psst sound periodically. i put a video up in my other thread. im thinking its pressure release at a carb boot but why is it building up pressure is my question. i may put some marvel oil in the intake ports and let them soak and brake up all the shit thats in there... i let marvel oil soak overnight and it runs a million times better minus this sound...im going to do a plug chop later and ride at higher rpms to try and blow some of it out
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Administrator
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If the floats are the same, and sit differently, see how the actual float valves look.
And the seats they slide in.
Maybe a worn float valve, some have nylon tips.
That would let excess fuel thru.
Those clamps/boots look great.
Some guys spray starting fluid around the boots when running, leak
will cause engine rpm increase.
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yea they only had two small tears and i repaired that. other than that they look fine. how would i seal them if they are in fact leaking?
im going to check and see if disconnecting the breather tubes from the box helps rid the pressure buildup. as well when i remove the box.
it sounds like the noise is coming from one of the boots maybe. so idk how itd be blowing or sucking in at the boots. ill do a closer inspection on the boots when i pull the box. i guess.
i sure do appreciate the responses. helps keep my diagnostic juices flowing when i can talk them out lol
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