Petew XS400 brat scrambler build

I installed the new battery and it cranks like a banshee. Compression is 154 and 157, I have spark but it still won't fire and stay running. I double checked valve adjustment it was still good. If I mist some starter fluid it will run briefly. Very briefly. I have tried switching coil leads and have established that they are where i want them, as the bike won't even sputter the other way. I am guessing that my problem is carburetor related so it looks like I start all over again with those...does this sound like a reasonable assumption to others? I am dying to ride this thing! HELP!!!
 
Well if it comes to life with starting fluid then I am thinking you are not getting fuel ?

Vacuum line hooked up ?
 
Yes, I checked that first...it has me stumped. I guess I take off the carbs and go through them again. I was certain that I had the problem when I re-adjusted the floats.
 
This morning I removed the carbs and put on a set from another 1980 G that I have and the bike started briefly and stalled, then gas flooded from the intakes- I assume the floats are stuck in the others. I visually looked at things again on the original carbs and the butterfly valves were opening at very different rates, I adjusted those by eye and will synch them if I ever get things running. Could the carbs being so far out of synchronization have caused this issue? After visually adjusting them it still makes no difference. I am going to go back through my valve adjustments-again! and then do a look through at the carb. I am getting spark because it will run briefly and too much starting fluid can produce flames if you don't let it dissipate. I know for a fact that cam timing was dead on during reassembly. Any suggestions would be welcome. It seems to want to fire when the throttle is opened but that results in loads of gas after a while.
 
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After playing with 4 carbs on the 1100 I always bench sync them now. Its easy and a good way to get the butterflys close. I even did it on the 400 when I took them off. I still need to sync them but it runs pretty good now.

Hopefully its something simple and you get it figured out.
 
I am determined to figure this out. I am becoming more confident that it is fuel related. I am dis assembling both carbs and , once parts get here, I am doing a complete overhaul on both sets. The second set was REALLY bad inside. I spent last night cleaning them enough to take them apart. I will need new choke plungers and seal for them along with all new guts.
 
Any news.............. :D
I have 2 carbs sitting on the bench, disassembled, waiting for parts to do a complete overhaul. It is all I can think of being wrong. I have spark, I have compression, the valves are perfect...it will start briefly with starter fluid...gotta be fuel delivery
 
I have 2 carbs sitting on the bench, disassembled, waiting for parts to do a complete overhaul. It is all I can think of being wrong. I have spark, I have compression, the valves are perfect...it will start briefly with starter fluid...gotta be fuel delivery

Hopefully they show soon......... I want to see this thing run ;)
 
Hopefully they show soon......... I want to see this thing run ;)
Nobody wants to see it run more than I do. Thankfully, I have extra parts and pieces ( you know how that goes...) and I can look at any extra as being readying the next build... for that one,.the motor is ready to come out but the PO stripped 2 allen bolts in the clutch cover. They are flush with the cover so you can't get vise-grips on 'em. I will be drilling them out tomorrow.... I have templated an electrical box too. I might try to make that while I'm waiting, never welded before but there is no time like today! Oh,.my blinkers all work now on the orange bike though.
 
Been busy already this morning. Overhauled 1 set and have another ready to go when the second set of parts arrive. I know these are done right this time.
 

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After 4 months and 5 days of screwing around, tearing down the engine, re-ringing it, lapping the valves,cleaning and rebuilding the carbs, and re-adjusting everything possible...IT LIVES!!! I have some tuning issues that I need to address, it pops on throttle roll off after reving. I haven't driven it yet because it is still stuck in gear and I don't feel like pushing it back up the hill. Now that it is running I will pull the other side cover off and look at the shifter assy. I hope it ends up being simple because I still have very little money invested to date. I feel like I have learned a library full of knowledge...but still so much to learn!!!
 
Congrats! it sure feels good when it fires up............
Sure does! I bought this in 2010 for $240.00 ran great but had a charging issue. I wasn't sure I was capable of fixing it so I put it aside. I had major heart surgery in 2011 ( Friday is the anniversary of my re-birth!) and developed wicked vertigo . I was afraid to ride so it sat. Looking back all it needed was a rectifier($14.68 used) and some repair to the choke mechanism. I paid next to nothing in all of my changes. $265.00 and I sold a tach for $30. I am all in at $475 bucks...I'd say I'm sitting pretty well for now. I hope the shifter problem is easy. I am afraid to go out with the bike to see if it will free up as I CANNOT push it very far, or up any sort of incline. By the way, I just stripped the wiring harness out of my parts bike to start plumbing up the next build. I had to do it- don't know what I would do if my hands weren't stained up with grease and grime!!!
 
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I have swapped out the main jets for 135's and got it going again. I have parts coming to fix the choke circuit plunger issue but it seems to be starting easier. I did find that I have an oil leak that I have traced to the camshaft seal behind the ignition. I don't see the plugs leaking and I is definitely in that area so I will pull the head and fix that too....I guess it's always something!
 
Starter enrichment system working properly now thanks to some nice parts I purchased from another of our Forum friends. I actually was able to scrounge around and found the ball bearings that I had lost on disassembly so I have a fully functioning choke on 2 sets of BS34 carbs. It is amazing how important that circuit is. Bike starts almost instantly when you hit the button now. I have been putting off pulling the side cover and clutch to look at the shift problem. When working outside the sun can be brutal these last few days. I will likely have to move into the basement if I need to get into things. I am going to drop the clutch and give it a try tomorrow. It is stuck in 6th, I believe, and I may need help pushing it back up the hill! She who knows all, sees all is here tomorrow-she can help!
 
I have swapped out the main jets for 135's and got it going again. I have parts coming to fix the choke circuit plunger issue but it seems to be starting easier. I did find that I have an oil leak that I have traced to the camshaft seal behind the ignition. I don't see the plugs leaking and I is definitely in that area so I will pull the head and fix that too....I guess it's always something!
Leak was fixed easily, the seal was tweaked a bit on assembly. I used as socket and eased it in where it was pushed out a bit. Ran it for 15 minutes with no indication of leak now.
 
Starter enrichment system working properly now thanks to some nice parts I purchased from another of our Forum friends. I actually was able to scrounge around and found the ball bearings that I had lost on disassembly so I have a fully functioning choke on 2 sets of BS34 carbs. It is amazing how important that circuit is. Bike starts almost instantly when you hit the button now. I have been putting off pulling the side cover and clutch to look at the shift problem. When working outside the sun can be brutal these last few days. I will likely have to move into the basement if I need to get into things. I am going to drop the clutch and give it a try tomorrow. It is stuck in 6th, I believe, and I may need help pushing it back up the hill! She who knows all, sees all is here tomorrow-she can help!

Sweet so you are good on choke parts then? If not let me know and there yours.

Get that thing on the road :D just take a cell phone and have a friend with a truck ;)
 
I got outside early today and took a look at the shifter issue with the bike. I removed the side cover and the clutch pack and the issue was glaring, when the potential buyer was here, stomping on the shifter, the c clip came of the shift shaft and allowed the shaft to move inward and push the link off the equalizer/shift pawl.(e6) I put it all back together and we have all the gears back. I had to reassemble the clutch and pressure plate assy. to line up the arrows and the rest fixed itself. The flasher I bought is a 2 prong, supposedly for LED lights but it doesn't do anything.... I can however ride it in the yard and side lot now! Waiting to license it now!
 

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