Fuel and Spark but no Start; 81 Special Cafe Project

[panman142]

After trying a few searches and not really finding what i needed, I figured ehh mine as well break the seal and make the first post....I just picked up an 81 Special a couple weeks ago as my first bike build project. It had been sitting in a garage for 20 years, everything was there, and the guy cut me one heck of a deal. Anyways, I started tearing it down to cafe it but wanted to get the ol girl runnin before I yank the motor out. So I cleaned the grounds up, stuck a new battery in it, cleaned the carb and repalced the float needle and seat so the floats actaully move now!! Also, replaced the coil, wires, boots, and plugs so shes got spark. Its got fuel, spark, and good compression but wont fire. It gives a sputter or two when cranking it with the electric start but after cranking for too long the starter gear hops off and "grinds" Its got fresh fuel and I tried some starting fluid but no luck. The petcock needs rebuild or replaced but I'm not too worried about that. But it will sputter and give a couple smoke puffs out the carbs or exhaust but thats it. Im not sure if the timing is off? I've done lots of work on cars and older enignes, i.e. im mechanically competent. Any help is greatly appreciated.

 

[NONclow]

Have you checked valve adjustment, and cam chain tension?
If you pull the plugs after it burps are they wet/flooded, or actually sooting up/firing at all?

 

[ogh11756]

Will it run on starter fluid?

 

[panman142]

I'm going to check the cam chain and valves tonight. And yes they are sooting up.
Thanks

 

[panman142]

And no it will not run on starter fluid, if I'm cranking it with the electric start and spray starter fluid in it, it like kicks the starter off the gear and makes that nasty griding noise, I think I read somewhere that there's an easy fix for that tho.

 

[scabber]

Welcome to the site. The 81 has a transistor ignition from the factory. Timing is controlled electronically if it hasn't been changed back to points. I take it you have read the carb guide. Set the float levels, bench synchronized the carbs ect. Are the carbs the BS 34. You normally won't get it to spark with the side stand down on the 81. Just trying to find out how much knowledge you have obtained so far. Do you have a service manual ?

 

[panman142]

Thanks! I haven't bought a manual yet, I've found most of (at least what I think) I need online... I have read through the carb guide and the general tips and troubleshooting/ no start write up. I did set the floats and bench synchro, pretty sure I did it right...but I've messed up before haha. And yes it's got bs34's and the factory ignition. I just wanted to get it running before I yank it for paint and such. I've tossed around the idea of just doing rebuild or re gasket, but the budget is kinda tight and I wanted to try to wait til next winter if I could. Gotta get her up and running before the riding season is over!!

 

[retiredgentleman]

You say you have spark, but that may not be true if you have not actually viewed the spark. I suggest you use a spare spark plug to make up a "test" spark plug. Use a piece of solid 12 gauge wire, connnecting one end to an alligator clip and the other end to the body of the test plug. A hose clamp can be used to clamp the copper wire to the body of the spark plug.

The alligator clip is clipped to a cooling fin on the engine, and the spark plug lead is connected to the test plug. A darkened garage is best to view the spark. A proper spark is blue not yellow.

 

[panman142]

Yeah I already did that. Just grounded one of the existing plugs and turned off the lights. It's blue.

 

[retiredgentleman]

Can I assume you are using full choke? Its also possible that the small orifice, for the choke fuel supply, that is in the bottom of the float bowl, is blocked. BS38 and BS34 carbs both have that small orifice, and it can be easily plugged.

 

[NONclow]

Type and heat range of plugs?
Sorry but my '71 has points ign (I love being able to file/adjust them by side of the road, if need be), not a costly TCI.

Switched wires/loose connection??
Vacuum leak??

 

[DogBunny]

Is your throttle open? It should be open a crack. Back out the throttle stop screw until it no longer contacts the lever arm. The throttle plates (some people call them butterflies) should be completely closed. Now, screw the throttle stop screw in until it just contacts the stop screw. Then, screw it in 3 more full turns. That is a lot, normal is more like one more full turn after contact, but with 3 turns you should get a very easy start (choke on). Be warned, that at 3 turns the idle will rev very high, so be prepared to immediately start backing the idle screw out again (or immediately kill the engine, back the stop screw out one turn, and start again).

 

[panman142]

I guess it's possible something may have gotten back into the choke channel. Yes full choke, ill check the throttle screw, I thought of that last night but forgot. Plugs are NGK Bp7es from mikesxs.

 

[scabber]

Page 31 of the carb guide shows the choke circuit in the bowel. Sometimes carb cleaner won't clear it. I probed mine with a strand of copper wire I think a strand of 16ga. Shine a light from the inside and look for light in the bored hole. Also those screens above the float needles. Have you pulled a the drain plugs and checked for fuel in the bowels. I read you were into muscle cars. I had a bunch back in the day. Still have the corvette. Float levels 22MM plastic floats. My 80 won't start if I twist the throttle It will back fire and not start. Proper starting procedure for mine pull out the black nob fully and hit the starter button. I would pull the carbs and recheck every thing.

 

[panman142]

I'm a Camaro guy myself. But anywho, yeah I replaced the float needle seat too. I used the rebuild kit from mikesxs. Hopefully those float bowl gaskets will still be good! But I'm gonna try to adjust the throttle screw and if not pull the damn carbs back out and go though everything again and re sync. Thanks for the quick replies, tryna get a game plan down for when I'm off work.

 

[weekendrider]

Go back over the carbs. The holes for the idle/slow circuit in the throttle body are easily plugged also. Sometimes requiring a pick to clear. Sometimes just compressed air.
I like to see fluid coming through them before I install.

 

[panman142]

Yeah that's exactly what I'm going to do. My air compressor died before so I had one of those stupid cans o air... Should help now that I got some power!!

 

[peanut]

I was going to suggest fresh fuel but I see you did that already.

If you have compression fuel and a strong spark but still no start , then I can only think it must be sparking at the wrong time

 

[panman142]

That's what I was thinking but if its controlled by the tci I would think I can change it, or maybe the box is bad?

 

[peanut]

I agree the Tci does sound like the most likely source . Maybe there is someone in your area you can swop one with