1979 Suzuki TS125 No Start - What Gives?

[KI4UJO]

I haven't been around here for a while (and sold my trike before I moved, for that matter) but you guys seemed like a good place to start, as there's a lot of enthusiasm for two strokes here. So, I bought this Suzuki around 2 weeks ago as a non runner. I had never owned a two stroke or any motorcycle beyond a minibike before, and it seemed like a good place to start. Pulled the cylinder to find it was in need of a rebuild. It was bored .50mm, now has a 56.5mm wiseco in it. OEM Suzuki gaskets were used for reassembly. Upon reassembly, it just wouldn't fire. Carb was cleaned out this afternoon. It does appear to have a strong spark as well. I ran a compression test (no choke,WOT) and got around 90psi, which seemed low to me,though the service manual lists a CR of 6.8:1.

Ideas? I've done plenty w/four strokes, but this is my 1st venture into the two stroke world.

The bike in question:

00k0k_dSR2oOpAHcg_600x450 by Jonathan Martin, on Flickr

00r0r_j9SDqotIohK_600x450 by Jonathan Martin, on Flickr

00U0U_9fx4RhDonH3_600x450 by Jonathan Martin, on Flickr

[El Camexican]

Are you sure you checked the compression properly? Lots of kicks with the carb wide open until the needle stopped climbing?

Do you have a way to tell at what point in the rotation the spark is happening? In other words, is the timing correct?

Also, did you put your hand over the carb and turn the engine over? It should feel like your hand is getting sucked into the carb.

Are you getting fuel? As in is the plug wet after many kicks?

Lots of things could be wrong, but as long as you have spark, good fuel and a strong vacuum when you kick the engine over it should be a simple fix.

[KI4UJO]

That is the exact compression technique I used.

Spark - I had the left cover off today - timing mark on the flywheel lines up with the mark on the case.

I have not tried my hand over the carb, I will tomorrow. Plug does not seem to be wet with anything other than 2-stroke oil (I would assume from the injection system).

I hope its easy - I'd love to have it running soon.

[El Camexican]

You can also try shooting some WD-40 into the open carb and kicking it over to see if it fires and runs for a few seconds. If that works I'd think your issue is fuel related. That compression does sound low though, but I know nothing about that particular engine. Does it have reeds, or is it a piston port engine?

[atc007]

Piston port,great little bikes! Who did your bore?Was your piston matched to your bore? When rebuilding ANY machine. Drain the tank,clean the carb, clean and oil the air filter,change the tranny oil.Know you are starting off fresh with a good crisp delivery of fuel. We can only guess atp,but it sounds to me like your bore job was not done correctly. 90 psi is when you tear them down to rebuild them,not the result of a rebuild. . Like el said, you can feed it ether,gas or wd through the carb and see if it pops.But 90 psi is not good.

[El Camexican]

Piston port,great little bikes! Who did your bore?Was your piston matched to your bore? When rebuilding ANY machine. Drain the tank,clean the carb, clean and oil the air filter,change the tranny oil.Know you are starting off fresh with a good crisp delivery of fuel. We can only guess atp,but it sounds to me like your bore job was not done correctly. 90 psi is when you tear them down to rebuild them,not the result of a rebuild. . Like el said, you can feed it ether,gas or wd through the carb and see if it pops.But 90 psi is not good.

Totally agree. unfortunately no one posts a photo of their tester, or what they paid for it, so we can never be sure if its even a valid test.

Jonathan, did you gap your rings? Set them on the pins with the netters facing up? Even if the piston fit was iffy the right rings should still give you some compression if the bore is straight. Compression will go up after break-in when the rings seat.

You can pour a cap of 2 stroke oil down the plug hole and test the compression that way too. It will go way up if the rings are too loose, or you have a scratched wall.