Yamaha AG 100 1980 - Won't start!

[AG100]

Hi All,

New to site ;)

I just bought a Yamaha AG 100 (Ever since I was young boy I always dreamt of buying a AG100!) I'm 40 now and finally bought one! The sad thing is... it won't start! The bloke who sold it to me said he got it started few years back but sat in his garage ever since. I bought the bike anyway... So when I got it home I drained all the oils and refilled. Also took the fuel tank off and clean that out using Apple Cider Vingar (youtubed it). Fresh oils, fresh fuel, cleaned carb... good spark... ENGINE won't start? Check CDI unit.. (new) Checked Coil (new).. Can anyone help?
Wellington
NZ

[onearmedbandit]

Spark - check
Fuel - ?
Compression - ?

[Akzle]

according to recent surveys, air is good too.

[Honest Andy]

Try putting the petrol on the outside, then apply match. That'll get it going for sure :laugh:

But more seriously...
check compression, then try a bit of ether
If it hasn't been started in ages the carbs probably clogged to fuck so next step clean the carb, especially all the jets. And the fuel filter.
but check compression first...
personally I think you've been had...

[AG100]

Spark - yes
Fuel - yes
Compression - Not tested (Don't have a tester, i'll buy one and test)

The other thing that bugs me is the rubber boot that connects to carb and air filter is hard as a rock and I feel air is def escaping.

[takitimu]

Spark - yes
Fuel - yes
Compression - Not tested (Don't have a tester, i'll buy one and test)

The other thing that bugs me is the rubber boot that connects to carb and air filter is hard as a rock and I feel air is def escaping.

Air escaping can't be a good thing, how are the reeds ?.

I reckon new robber boot & possibly reeds before compression testing ( though no pressure hand pushing the kick start would be a bad sign ).

You've got a good spark & clean carby, so it's really air intake & compression at this point ( did you clean the breather pipes for the carby ? ).

Oh, don't be scared to start it in the garage with no air filter ( assuming it's not dusty ).

[FJRider]

Spark - yes
Fuel - yes
Compression - Not tested (Don't have a tester, i'll buy one and test)

The other thing that bugs me is the rubber boot that connects to carb and air filter is hard as a rock and I feel air is def escaping.

Seeing a spark is one thing ... but a good spark is needed if other issues (like low compression or air leaks) are involved. Try a KNOWN good spark plug (if only just to compare the spark without actually screwing it into the head) and try. Check the plug lead isn't shorting out.

Engines low on compression can often be bump started ...

[Scubbo]

got oil in the autolube under the seat too? that not blocked? could try premix

[mickmackmike]

I have the same issue....
Have Fuel,,,
Have lots of Spark,
shot ether down,,
purchased another carby.

At this stage I have no idea....
I did check the reeds before they looked fine..

Not sure what I have missed here.. ODD...

I don't have a compression tester, but yes will give that a go.

The Ag100 was sold as sat for a few years as they couldn't figure out how to get it to run again.......

I have had the thing started and running fine after changing coil spark plug and carby all at once,,,,,,,, but now I try to start it after a week and nothing...
really strange.
Add fuel and spark,,,, even spray ether down the spark plug hole and put the plug back in and nada....

Mike.

[Ginge09]

Crank seals might be stuffed. Will lose you compression.

[mickmackmike]

As I couldn't find this info anywhere else idle air screw is listed in the service manual as 1 1/4 turns out. Didn't realise I had a service manual, but it says it is one,,, very basic I tell you.

i cleaned the carby again, but I don't really understand why it ran in the first place, then didn't run, and now runs again.

I have the bike running but cannot get it to idle properly.

idles fine, when you go to rev it it will not return to low idle,,,, even though the throttle slide in the carby goes all the way down,,,, kind of makes it feel like there is air getting sucked in somewhere........

The bike seems to run okay, although gutless, and a little hard to start,,, given it's an old bike I think it needs rings.

I have two carburetors an additional one that I purchased,,,, having the same issue between them on the fluctuating idle,,,, is difficult to make it sit continuously on the same idle,,,
any thoughts on the answer appreciated.

Mike.

[mickmackmike]

Crank seals might be stuffed. Will lose you compression.

I will get a compression tester,, haven't checked against the manual but should state the compression specs....
Other than that I will order new reeds just in case,,, as that could be something else that could make it loose compression I guess.

AFTER stripping the carby AGAIN!!! triple checking every passageway and jet,,, I was able to get the bike running continuously running on the choke, until you would take the choke off try to idle it down and then it would just die,,,, put the choke back on and It would could keep running again,,,,
- went back to the manual to find the idle fuel/ air adjustment 1 1/4 turns
- really contacerous as while I could try to set the idle screw screw every time I revved it it would not return to the same spot.
- stretched the spring a bit more, ensure that the throttle slide piston returns all the way down and it does,, double check freeplay on throttle etc,,, returns 100% every time down,,, but yet the idle doesn't return down..
Strange.

Wondering what else might be effecting things.........
Was thinking maybe the reeds arent' doing what they are supposed to do after reving the bike,,,???????????


I blocked off the post mix hole in the carby, put premix in the tank and I could be wrong but seemed to be better,,, to the point I could idle better without choke

[Ginge09]

. I was able to get the bike running continuously running on the choke, until you would take the choke off try to idle it down and then it would just die,,,, put the choke back on and It would could keep running again,,,,

Wondering what else might be effecting things.


The other thing that bugs me is the rubber boot that connects to carb and air filter is hard as a rock and I feel air is def escaping.


Mate, that'll be that air leak. Bike is sucking air, you pull choke on to richen it up, it runs okay but dies when you turn choke off.

Bike not returning to idle is the same issue. It's sucking air so runs lean and revs high.

Change that boot before you start spending money on reeds. In the short term wrap some tape around it to see if it improves things.

[F5 Dave]

Pull the boot and reed block while you are at it. Reseal with something like Loctite master gasket and or cut new gaskets then put back together after careful inspection of said boot
It will only take a small leak to do that. I was going to mention oil injection point. Carb shouldn't have vacuum tap connection but that is always a favorite. Inspect reeds while you are there.

Look under left cover for sign of oil seeping from behind flywheel ie left crank seal.

[mickmackmike]

Pull the boot and reed block while you are at it. Reseal with something like Loctite master gasket and or cut new gaskets then put back together after careful inspection of said boot
It will only take a small leak to do that. I was going to mention oil injection point. Carb shouldn't have vacuum tap connection but that is always a favorite. Inspect reeds while you are there.

Look under left cover for sign of oil seeping from behind flywheel ie left crank seal.


I agree and I sat there with the same diagnosis a few weeks back.
Took the reed block out inspected, put it back with gasket goo just to be sure,, inspected the reeds.

In my head I am thinking it has to be sucking air in somewhere,,, then bingo, I said to myself I forgot to put the oil injection tube back in....
But when I checked I had...

I wil go through it again, ordered reeds and gasket, and will start over with the diagnosis for an air leak...
Maybe the reed block has a crack I didn't notice, but I thougth I had a good look...

Maybe will need to check any vacuum on the carb???

Mike.

[Ginge09]

Spraying a bit of WD40 or something around the boot when it's running will help locate the leak. It'll breifly seal the hole and you'll hear the engine note change.

[mickmackmike]

Agreed I had tried this but there was no change,,,
Kind of why I thought maybe it was the reeds?
or some other issue. On a DRZ carby there are vacuum hoses and all sorts of things on the carb but this is a really basic carby,,,, maybe it is a crankcase leak like someone suggested here.. I guess I could spray around the engine while it is running and see that,,, I don't see any oil leaks off the engine crankcase though..

Whenever you buy a bike off someone who spent hours trying to get something to run properly you always figure it was them,,,, but yeah a little bemused as I feel like I have been pretty good on my troubleshooting diagnosis.

Mike.