the carburetor catastrophe

8/6/2012: about two months ago i decided to try and fix a small problem with the idle that had developed hoping that it would also cure the problem that had been around since i had become the owner. the small problem: after about 10 or 15 minutes into a ride when i came to a stop the bike would die. it took a few tries to start, and it seemed that if i was downhill, the bike was harder to start. but, it started and it did not ever die a second time. the rest of the ride was fine be it a half hour ride, or a 3+ hour ride.

that was annoying. the bigger problem i hoped to solve was the initial start and warming up. choke was useless while starting. i had to open the throttle about one quarter or more. then i had to sit and hold it at 2000 rpm for 5+ minutes until it had warmed up a bit. really, it was best to hold for nearly ten, but i found that i could take off at 5 minutes and when i came to a stop give it a bit of gas so it would not die. by doing this i did not have to sit for 10+ minutes warming up the bike and after about two minutes on the road all was fine (until stopping at the 10/15 minute mark <g>).

while first testing this out i blew the end cap off and tried fixing it. the end cap fix has worked well. i took the baffle out just in case that was the cause of the problems that started to develop...

once everything was put back together the bike was basicallhy a PITA to start. i honestly don't remember what the symptoms were at the time. but i ended taking the baffle out, cursing, and cleaning the carburetor. once this was done everything was theoretically clean and the jets and floats were set back to spec. it should work... then when i started it up everything seems ok until it got warmed. when i revved it, not only did it not fall back down, it climbed to about 4000/5000 and hung. i could turn the idle screw and this would make it decrease, but then it would die.

the first thing that pops into everyone's mind is the butterfly shaft valve seals! but these were replaced last summer! then, the boots. no cracks, soft, pliable and they seem fine. i tried spraying WD-40 and found no rev increase anywhere. something was not right! when i took the spark plugs out the body was very dry and black, just like being rich. but the ground strap was white! it must be lean.

with a bit of futzing i was able to get it to idle, but usually this involved strange things like the idle screws being 3 1/2 or more turns out, the idle jets being larger than the OEM 42.5, or the floats being in a non-standard position. on top of this the plugs would be jet black and the bike would not really idle smooth.

ok, after starting i found you are suppose to start from the top down: wide open throttle, 1/2, 1/3, then idle. but, at this point i could not even get the bike to idle well without dieing!

it was somewhere around here i decided to try the balloon trick to see if the carb was sucking in air since i could not hear any change using WD-40. i didn't want to use anything else in case the seals were fine and end up ruining them. it didn't look very good...

left side before
right side before
left side running
right side running
there was definately an air leak. after a bit more messing around i decided to use carb cleaner to test the seals again to see if i could make it rev. i was going to order new ones anyway, so it would not matter if they were destroyed. interestingly, the carb cleaner made it rev! could it be that because it was so rich, WD-40 did not have the same effect? or maybe carb cleaner causes a higher rev and is just easier to hear?

when ordering the new butterfly shaft seals i also decided to replace the choke gaskets. i usually see them referred to as "dust seals", but at this point i decided that even though they were a loose fit, i did not want to take the chance of them leaking air as well. gaskets and seals can collapse when malleable, but after more than 30 years they tend to harder up a bit. <g>

they were a bit hard
by this point i had replaced almost everything i could think of and cleaned and cleaned and cleaned and cleaned... the carb was back to speck, except for the main jets. the bike has pods and everyone on the forum who has posted carb info i remeber reading about uses one size larger: 132.5, so that is what i put in. the hope was one less thing to change.

i put it all back together, on the bike and fired it up. bang! it started off pretty darn well for a 97 degree day. while it warmed i adjusted the idle screw a bit since it was still in the previous postion. the revs all fell back down and did not hang! i was very hopeful. then it was time to stop.

another issue caused by the leak that seems to have been solved was a temperature difference. i have one of the hand held laser temperature devices and i was using it to try and make sure the bike would not overheat (really, i do not know how hot is bad, but if it gets really hot despite the fan, i would turn it off). i would take the reading of different places, especially the exhaust. doing this i notcied that the number three exhaust was 150+ degrees cooler during idle than the other two. when revved to 2000+ it was about equal. after the seals were replaced i found that the temperature on all three are about equal whether idling or revving. interesting...

the next round of testing began. once again it started fairly easily and warmed quickly compared to before. when i revved it, it did not linger, but fell quickly back down. i synced it and took it out for a test run! the ride ended up being only about 40 miles, but it was great! no hesitation! it did not die! and when i got back i took the plugs out to see what state we were in:

after about 40 miles
one-left-1161   two-left-1149   three-left-1150
one-right-1151   two-right-1152   three-right-1154
i did not stop along the way, this is just a look after the ride. but, according to everything i found, these should actaully be about normal! (here's the ngk page) we will see if the problems are cured, but i have high hopes! i will probably decide to do a bit more testing, but for now it's finally time to ride again!

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last major update: 9/6/2016