facebook1   youtube1   twitter1   instagram   linkedin1   pinterest1

logosmallNOTICE:  If you are not a free registered member of the site, you will not see the photos in the forum, and you won't be able to access our premium member content. Please consider joining our community!

Yamaha GT80 Sparks but wont run

13 Jan 2020 17:54
Fewmarshall
Novice
Novice
Posts: 44
More
Topic Author
Yamaha GT80 Sparks but wont run #1
So here's the scoop, finally got the bike sparking after buying a second ignition coil (not from china this time). I sourced a new gas tank off ebay and also got a new fuel valve, new fuel line, and a new carburetor. Head gasket, clutch side gasket and intake gaskets all replaced. New air filter and contact points&condensor on the way.

I could tell that the engine was firing weakly while kicking, so I brought it up a hill and bumped it down in 3rd, tried 2nd but pretty icy here in Canada right now and just slid down the hill. The bike fired up and poofed some smoke out the exhuast but it will only go 10-15 feet bogging out before stalling. Could this be because I wasn't gaining enough speed to bump into 3rd? the hill I used isnt very large. Took out the spark plug and repeated the test several times - the plug was soaked every time.

I get good looking blue spark while checking outside the engine, but I have read that a weak spark might not happen at all under the compression of the engine? it would only run bogging very hard with no throttle response for 5-10 seconds each time before needing the spark plug dried off again (brand new plug) I tried fiddling with the mixture screw with no results and ended up leaving it back where it was. It seems that either the spark is too weak to ignite the gas or it is getting flooded with more gas than it can burn.

I noticed when installing the throttle cable to the carb slide that the needle clip was set at the lowest position, which I read means rich, should I move the clip to the middle and see if leaning it out helps a bit?

The bike hasn't ran at all for over 5 years, so I'm very excited to finally have spark and small signs of combustion, any help is muxh appreciated! This is the first bike I've ever worked on so I'm pretty new to this.

This message has attachments images.
Please log in or register to see it.

Please Log in or Create an account to join the conversation.

14 Jan 2020 09:13
Fewmarshall
Novice
Novice
Posts: 44
More
Topic Author
Yamaha GT80 Sparks but wont run #2
IT RUNS!!!!! fiddled with the plug gap and the points timing and it fired up on the 4th or 5th kick... carb still needs tuning but it idled on its own for like 15 minutes before it stalled :) took it on a little ride after that shifts through all the gears nice and throttle response is pretty good :)
The following user(s) Liked this Post Gr8uncleal

Please Log in or Create an account to join the conversation.

15 Jan 2020 12:04
Fewmarshall
Novice
Novice
Posts: 44
More
Topic Author
Yamaha GT80 Sparks but wont run #3
Leaky shift shaft and pushrod oil seals.. anyone know a good site to get them off besides ebay?

Please Log in or Create an account to join the conversation.

16 Jan 2020 05:43
Camp3
Site Supporter
Site Supporter
Posts: 154
More
Yamaha GT80 Sparks but wont run #4
Partzilla seems to have a lot of stuff, Rocky Mountain ATV, Speed and Sport in Bloomsburg PA for the rarer stuff...

www.partzilla.com/catalog/yamaha/motorcycle/1974/gt80a

1976 DT175C
1975 DT100B Kid Trainer
1974 DT250A In Process
1992 FJ1200
The following user(s) Liked this Post Fewmarshall

Please Log in or Create an account to join the conversation.

16 Jan 2020 06:35
Fewmarshall
Novice
Novice
Posts: 44
More
Topic Author
Yamaha GT80 Sparks but wont run #5
Thank you!

Please Log in or Create an account to join the conversation.

Moderators: yamadminEnduronutMakotosunDEETVinnieDevinJames Hart