I need a little bit of help to get my 1982 Pantah 500TL running and idle for more than 5 seconds. I bought the bike with a 2-1 open conti exhaust and it ran quite ok. I got a set of stock exhaust with the bike and last year before the winter lock up I decided to install them to make her 100% original. With the stock exhaust I also fitted the stock air box as with the open exhaust it had a mesh only. The bike ran acceptable at the time but I never rode it instead I parked it for 4 months. Now spring is arriving and I wanted to take it out finding it is unwilling to start but when it did it needs a very warmed up engine to get it to idle at around 900rpm and but see it stalling after 15 seconds. I guess its rich. I fidled with the mixture screws ( is it normal that the front is almost unreachable due to the frame?) and found the rear carb 3,5 turns out and the front 2,5. I set them both at 1,5 as a starting point but that didn't work very well so I started fidling with the idle screws and now I am deep in the woods as it does not run any better and I have no idea where the idles crews are set. is there, like with the mixture screws, a base setting?
I’d check the pilot jets are not blocked first. If it had an open exhaust and airbox then it was probably set up to run those so it will need rejetting back to standard for the now standard set up. Also put the mixture screws back to standard settings and go from there. Ive not worked on a Pantah but carbs are carbs.
Pilots are stock. And I believe they are all the same 500, 600 and even the 650 Allazura. I removed the tank and tried to rotate the front carb so I could better acces the mixture screw. Unfortunately the float bowl prevents any usefull rotation. However I was able to rotate it a tiny bit so I could now really turn the screw fully home and then 1.5 turns out. it was also, like the rear about 3.5 turns out. It would really be usefull if there was a idle screw base setting. Or can I see the slide and screw action if I remove the intake rubbers?
But are the pilots jets blocked? It doesn’t take much for them to get gummed up as the holes are tiny.
Std setting assumes you are running 4 star leaded so not much use. On these PHF 36 the screws are mixture screws, on VHB for example they are air screws. Std setting is 1.5 turn out from fully in. If for example you found they need to be 3 turns out you would need to go up a size on the pilots and return the screws to 1.5 turns, going 5 points so say from a 60 to a 65 pilot jet is about 1.5 turns equivalent on the mixture screw. To set the screws find a setting where you have a tickover of some sort atr 1.5 turns out by changing the jets. Once you have a tick over, wind one screw in till the engine faulters, wind it out again till you have the highest revs achievable and then back the screw back in a 1/4 turn . do this with both carbs then adjust the overall tick over with the throttle slide screws evenly on each carb. Better still use some vacuum gauges. If you are not sure if its stalling because its rich or weak try giving it a little choke as it starts to faulter and see if it picks up. If it needs the screws further out its running weak as you are richening by winding screws out.
I'm afraid the bike would not even start having fidled to much with the idle screws. I have now set them fully home and 3.5 turns out. I read this number somewhere on the net. But in any case I wil remove the filter hoping to be able to see the postition of the slide. I have a vacuum gauge which might fit the belmouth. I'l report back.
Yesterday evening I pulled the carbs and removed the float bowls. All jets seem to be the originals. I placed all jets and accellerator pump parts in my ultrasonic cleaner. After this work it seemed both pump jets where squirting fuel. I set the slides roughly equal with a drilbit of 6.5mm as some kind of base setting. Mixture at 1.5 turns out. The bike ran but had a sluggish pick up and idle revs seemed to float around 2000rpm after the throttle was blipped and slowly the rpm dropped until it stalled. After a lot of fiddling with all four screws I ended up with a mixture screw setting close to 2.5 turns out and with my vacuum gauge I could set both slides in sync. It idles for several minutes but still has the tendency to stall. I raised the Idle rpm to close to 1500rpm and now it idles stronger. I'l leave it like this for the moment and go out for a ride later today. Thanks to all for your advice and guidance. Cheers, William
One other point with PHF carbs. make sure you have slack in the choke cables so you are 100% sure the chokes are shutting fully. Also check the end of the choke pistons. They have a rubber bung in the end. these should be flat. If they have gone hard there will be a nipple in the rubber bung and the chokes will not seal shut. this will cause it to run a rich and give you an uneven tickover that gets worse when its hot.
Both plungers seem recent. No pronounced bits. One last question: what is in general the best cold starting procedure for the Pantah? My bike is parked in an indoor garage, hence always at room temperature. I use no choke, just a few twists of the throttle, but it takes a long time to fire up. It seems to fire only when I release the start button. And when it runs it needs a long time for it to idle
Sounds like the voltage to the coils and ignition boxes is dropping while the starter is cranking. This mod that I posted in another thread should help.
Basically a relay releaving the starter button from passing current. Smart! I'm mostly into classic Italian cars and also there relays where hardly used, so electric windows or lights would run directly through the switch. Thanks for sharing. W
