Hi all.
My '85 Aero is still having start difficulties. I've replaced the piston rings and head gasket and *still* have compression at 90psi. Reed valve looks fine.
I'm concerned, though, that the compression reading isn't correct. I have plenty of power (unless it's a steep hill, then it gets sluggish) and it's quick on takeoff. It just won't start without starter fluid if it's cold. Bystarter tests fine. Once it's warm, it cranks right up.
I'm installing a new cylinder gasket soon, so maybe that's the problem. Anyone have any thoughts about why my compression would still be 90psi after changing rings? Piston and cylinder are in fine shape. Carb has been cleaned and re-cleaned and re-cleaned. It also seems to have a small leak. I see gas accumulated near the drain screw. New carb gasket is on the way, as well.
Anyway...A new problem has emerged:
Once it gets warmed up, the scooter makes a strange air puff sound when I give it throttle. It makes a weird "pfft pfft pfft" sound, one "pfft" about every half second. Sounds like someone is making noise with an air compressor.
Anyone have any ideas what this might be?
'85 Aero Mysteries...
Moderator: Moderator
Low compression: If you have a compression tester with a long hose and the compression release is near the gauge, these will read low, esp. on low displacement engines. Otherwise you're running rings that are too small for the bore, poor seating, etc. It it has good power I'd let it go for now.
Pfft Pfft noise is probably exhaust towards the back (front makes ticking sound) or intake.
Pfft Pfft noise is probably exhaust towards the back (front makes ticking sound) or intake.
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The rings *should* be the correct ones for this scoot, although the kid at the Honda shop did some kind of crazy 3-card-monty with them and a set of rings for an '86. But the '86 rings didn't work (top one wouldn't even seat; bottom one seemed to fit fine). I've got the correct rings on there, now, I think.
And thanks for the heads up about the compression. I have a foot-long hose. Is that enough to make it test 20psi+ too low?
The pfft pfft sound *seems* to be coming from the left side of the bike around the carb. I'm hoping that it's connected to one of the two gaskets I'll replace this week.
Thanks!
And thanks for the heads up about the compression. I have a foot-long hose. Is that enough to make it test 20psi+ too low?
The pfft pfft sound *seems* to be coming from the left side of the bike around the carb. I'm hoping that it's connected to one of the two gaskets I'll replace this week.
Thanks!
Just a quick note to say that I covered the carb air intake with my hand and the bike fired right up and remained running. I've got a carb gasket kit on the way as well as a new cylinder gasket. Am I right in thinking that the bike starting under these conditions points to too much air in the carb (i.e. possibly allowed by a bad gasket)? If the new gaskets don't fix this, am I right in thinking that the other culprit is a bad bystarter?
if you cover the carb and the bike starts you got an intake leak, could be anything from bad seals to intake gaskets etc
Try cover the carb with the engine running and spray wd40 or carb cleaner and even brake clean all around where the gaskets and seals are, if the bike revs up or dies- depending on what you use ,in the area that the idle changes is your leak
Try cover the carb with the engine running and spray wd40 or carb cleaner and even brake clean all around where the gaskets and seals are, if the bike revs up or dies- depending on what you use ,in the area that the idle changes is your leak
I sprayed around the cylinder gasket and the carb and got nothing, but then, I don't really know where I'm looking. Which seals? Which intake gaskets?W/C wrote:if you cover the carb and the bike starts you got an intake leak, could be anything from bad seals to intake gaskets etc
Try cover the carb with the engine running and spray wd40 or carb cleaner and even brake clean all around where the gaskets and seals are, if the bike revs up or dies- depending on what you use ,in the area that the idle changes is your leak
I'll poke around on it a little tomorrow.
Thanks for the advice!
OK. I noticed that the plastic heat gasket thing between the intake and the carb was actually on backwards (O-ring towards the carb). Managed to strip the carb mount re-installing it, so I won't be able to test it until I can tap it out and get a bolt in there was a snug seal.
Anywhere else I should check?
Anywhere else I should check?
