Won't Idle, Supertrapp, and weird jetting. UPDATE #3

So the newly acquired 82 Seca 750 won't idle. I figured it was from sitting for 3 years, but i went through the carbs today and they were in rather good shape. I even polished my emulsion tubes so they look like Rick's little pic of nice tubes

I did find some odd jets in it tho, along with an exhaust oddity. I'll start with the Supertrapp exhaust on it. It's a 4-1 and had 19.. yes.. 19 discs in it. Seems in good shape tho. The fuel pilots are all #43 and mains are #120.

Now air jets. They're all #80 and #195 but i'm not 100% sure they were in the right spots. My 400 doesn't have the two air jets under the hat so this is new to me. Looking at the engine side of the rack, the jets sit on the left side of the carb top. The #80 was the farthest away, the #195 was the closest to the engine side.

Is this correct or are they backwards.

The idle problem is this, RICH RICH RICH, to the point i almost smoke myself out of the shop when it's running.

If i blip the throttle it'll pick up and shoot to 4-5k rpm, then slowly fall to 500-800 rpm and die eventually.

Is the #80 supposed to be the pilot air, and the #195 the main air, or is it backwards. The manual says it's supposed to be #225 pilot air jet and #80 main air jet.

Would a #43 fuel pilot and smaller #195 make the bike act like this?

It's very odd that the Supertrapp had 19 discs in it, aren't you supposed to have like 8-12 for a good tune. With 19 it should have been running leaner than all get out.

What am i lookin at boys?

EDIT: I did find THIS post:
http://www.xjbikes.com/Forums/viewtopic ... r+jet.html

Where Chacal cleared up my jet size issues, seems all is good for up here in the north.

Just need confirmation on if those air jets are switched under the hats.

I also found a post where Rick cleared up my question of air jet order, bigger jet closer to engine side, smaller for main air jet. Grrr i was hoping it would be as easy as jets backwards.. i guess not lol.

 

Re: Won't Idle, Supertrapp, and weird jetting.

i have a MAC 4/1 and a 4 inch supertrapp i'am running 7 disks and 126 mains 40 pilot, stock filter and airbox

 

Re: Won't Idle, Supertrapp, and weird jetting.

Oh ya, i'm running stock filter and air box too. Thanx for the setup info Pol!

Gives me something to go by

 

Re: Won't Idle, Supertrapp, and weird jetting.

Yep, sounds like the same problem I'm having! And I KNOW it has got to be something simple...

When mine would bobble at about 500-600 rpm before it dies, I'd adjust the main idle screw in an attempt to up the idle rpm's...but I'd keep turning it in and nothing would happen until it shot up to 3k rpm.

You may be on to something with making sure you've got the correct jets -- I haven't checked what I've got but I should probably do that. Everything I've done so far just tells me it's something with the pilot jet. The PO said it was stock, but you never know.

 

Re: Won't Idle, Supertrapp, and weird jetting.

Ya i'm not 100% on which air jets were where, so i'll definately be checking that first thing next Monday. I'm hoping i'm remembering wrong and that's all it is.

I could see how someone could get those backwards.

 

Re: Won't Idle, Supertrapp, and weird jetting.

So i got to check the air jets tonight. They are in the correct positions, so i'm a little baffled. One thing i did find tho.

The plastic ring that holds the rubber diaphragm to the piston bore, on 3 of the carbs, is cracked (on the top side, the bottoms are fine, and i mean like it's broken right through in one spot so it's not a complete circle anymore, kinda like this: C instead of O). I'm going to assume that this will play havok with my pistons not reacting properly to vacuum?

Also my clearances were pretty tight, i have to change all 8 shims. They were only out by one or two shim sizes tho.

I think what may help me troubleshoot is to take Dezi's carb rack off his running good bike and try em on mine and see what it does. If it runs good then i know my carbs are fubar'd, if it's the same i've got bigger issues than i thought lol.

So are the rings on the diaphrams toast? or can that be quick fixed with RVT or something so they don't leak?

 

Re: Won't Idle, Supertrapp, and weird jetting. UPDATE #1

The plastic diaphragm retaining rings commonly split as you've described; it doesn't seem to cause a problem.

There was a discussion about them a while back, it seems a lot of folks have cracked rings and have had no problems. I tried searching for it to no avail.

Two sizes on a shim is a lot tight.

 

Re: Won't Idle, Supertrapp, and weird jetting. UPDATE #1

Ya i'm gunna replace em of course before it's on the road Fitz. I was just reporting everything i find in this thread to maybe get some more ideas on why this thing is running like poop

Good to know the rings shouldn't be an issue, i was worried cause the gap is like 1/8" but i havem't really looked how they're attached so i didn't know if it would mess with the vacuum at all.

Thanx for chiming in Fitzy!

 

Re: Won't Idle, Supertrapp, and weird jetting. UPDATE #1

**UPDATE**

So i got a couple things sorted out today: signal lights now all work, horn works.

I replaced the tight exhaust valve shim so it was in spec, and used the one that was in that bucket to fix an intake to be in spec. (It's a holiday here so nothing was open to get a full set of shims).

Threw her back together and started her up.. Definitely idles better, but still hangs at 3-4k rpm sometimes. Then i noticed something...

It was a very faint backfire which sounded like it was coming from the floor, so i got my head down there and looked. Where the 4-1 was coming together, i could see a faint flame when it popped. Then i noticed the PO did a half ass job trying to seal something in the exhaust with some kinda of fiberglass like stuff.

Needless to say, there's definitely a hole in the exhaust before the muffler. so i could be running really rich when idling and really lean when ya open the butterflies a touch.

Exhaust will come off tomorrow and i'll get a better look at it, but i'm hoping that this is the issue with the hanging idle. New plugs will be in order too as the old ones are of unknown quality.

Also i did find a plug cap that was bad so that will be replaced tomorrow (borrowed Dezi's for test running today, prolly why i got the better idle)

On the plus side of today, Dez let me take his 750 home man i love how these seca 750's run when they run right

I have bench sync'd, but not bottle sync'd, and i haven't probed for leaks with propane yet (don't have any) but we do have some starter fluid, i'm just scared to blow the bike up if it catches lol I may try quick sprays of that on the throttle shafts tomorrow and see if it reacts. Intake boots are cracked on the outside, but not all the way through so it's not them.

Will update tomorrow night with what i find tomorrow.

 

Re: Won't Idle, Supertrapp, and weird jetting. UPDATE #2

**UPDATE**

So i got new plugs today (apparently NGK doesn't make the BP7ES without the "R" anymore.. or so i'm told..) So i got a good idea of what the mixture was like at idle. Turns out 2 turns isn't enough for my baby yet. 4.5 turns out and away she went, idles pretty good, doesn't hang up anymore. So i'm pretty happy.

The truth will be told when i take her up the street a few times and see how she'll react under load, and some seafoam through one or two tanks should help out as well (top of the pistons were pretty nasty looking)

More will come as i find out But it's looking like it's Kev - 1 Seca - 0 lol

 

Re: Won't Idle, Supertrapp, and weird jetting. UPDATE #2

By who? I think I'm pretty save to call bull, every forum, every person, dog, cat or fish with an 80's bike (or car)refers to those plugs.


So ur running the R's now? That might just open a whole new can of whoopass.

 

That was from a Yammy dealer Could be bull and they just don't wanna carry them, but it was impossible to find D8EA's that weren't resister for the 400 as well. They told me as well, that NGK is going to stop making plugs with the removable cap as well.

So i'm running R plugs and 5k caps at the same time right now. Doesn't seem to run bad so time will tell whether 10k resistance at the plugs is too much.

Oh ya, and i ran her up and down the street a few times. Runs STRONG! i'm quite pleased. The only thing I noticed, is that i think it may be slipping the clutch a little. I know i need a new clutch handle as it's been bent a little and is really floppy/sloppy. It very well could be just that it's sat for 3 years as well without running, and i ran her up to 6k first run out

Vid and pics to follow

 

Pics:
http://www.flickr.com/photos/krsthis/se ... 648451442/

Vid:
http://www.youtube.com/watch?v=CftRnsn-HNE

You can see the sealed battery I got was 1/2" too wide for the compartment, it does fit behind the side panel tho.

This winter will be the new paint, clean up everything phase. Not sure what colour yet. I'm wrestling with burnt copper, or a purple, or a dark sorta british racing green.

 

CanadianTire carries them less $3 a pack(2)