Author Topic: 2 Stroke suzuki JR80 tuning help (Read 17863 times)

ThomasD883 · « **on:** November 10, 2011, 06:28:32 AM »

Hello everyone, thanks for looking. I recently assembled an 01 suzuki jr 80 that i got in a wet carbaord box completely dissasembled. Fast foreward and its assembled but will not run correctly. My main issues are that i cant get it to idle even when hot no matter how much i F@$# with it and that with the choke on when it starts it revs about as hard as it will go. I have been over the carb with a fine toothed comb, all of the carb settings are at stock, replaced the piston and rings, replaced the plug, and checked for air leaks or restrictions, exhaust restrictions. Any advice is welcome cause the next step lands it in a deep lake

. Thanks

FuZZie · « **Reply #1 on:** November 10, 2011, 03:33:49 PM »

Make sure the spark from the plug is in the bright blue range, my suzuki 100x2 was doing the same thing before the coil went completely dead.

ThomasD883 · « **Reply #2 on:** November 11, 2011, 07:35:54 AM »

Thanks for the reply! I removed the plug and checked for spark.on the engine case and got a nice blue spark, correct gap. Checked the timing on the wheel as well, it too is set exactly on.

ThomasD883 · « **Reply #3 on:** November 11, 2011, 07:39:29 AM »

This carb has a weird choke, it like a plunger instead of a flap and the air hole is about the size of a pencil. I've never fiddled with a two stroke before, are they supposed to rev real high with choke on?

FuZZie · « **Reply #4 on:** November 11, 2011, 08:18:04 PM »

no, It seems a bit faster but not what I'd call really a high rev thing.
I'm not sure on your choke, can you do a pic?

Leino · « **Reply #5 on:** November 11, 2011, 11:34:45 PM »

Make sure this isn't one of those carbs you can put the slide in backwards by mistake...

ThomasD883 · « **Reply #6 on:** December 16, 2011, 05:51:46 AM »

A'IGHT, im back with pics.The two with the blue circles show the choke inlet and outlet , the outlet is pretty hard to see but its as good as i could get it.
Lenio- I'll try flipping it around and see what happens
Thanks

seanbarney41 · « **Reply #7 on:** December 16, 2011, 06:32:56 PM »

even though it is still commonly referred to as a "choke", I think it is more accurately referred to as an enrichment circuit...instead of choking off the air to make the bike richer when cold, it opens an extra amount of fuel for the same result....I think...unfortunately, i have the same two stroke learning curve to overcome as you...

Goofaroo · « **Reply #8 on:** December 17, 2011, 04:53:29 PM »

If you are certain about the carb being assembled properly then I would suspect an air leak. Two strokes are in general very simple engines but they will not tolerate air entering the case without first being metered by the carb. You say it only does this when it is hot. Is it very easy to start and idles well until it is warm? If you snap the throttle does it quickly return to idle until it gets hot?

ThomasD883 · « **Reply #9 on:** December 17, 2011, 10:59:52 PM »

Thanks to everyone. It will start with choke/ enrichment on ( thanks for the tidbit there I'm learning on the move) but idle high, and I basically cannot achieve a low idle. I did not try a reed valve as it seemed crisp and was not damaged, is that worth theowing one on to see. Any advice is welcome, much appreciation.

Goofaroo · « **Reply #10 on:** December 18, 2011, 06:29:08 AM »

If your reeds look to be in good shape then they are probably fine. I would suspect that the carb is not right or that you have an air leak. Did you reassemble the carb with factory jets or did you use aftermarket jets from a rebuild kit? Are you certain that the carb is clean through every passage? As for the choke, it should be fairly simple to see if it is operating properly. There isn't anything to the choke other than the plunger traveling through the bore so it should be able to tell whether it is working or not. If it is, then the question remains as to whether or not the carb is assembled correctly, has the right parts, and is clean. I know how maddening it can be when you have problems like this but the answer to this puzzle is right in front of you so hang in there.

You said that you have checked for air leaks. It is easy to check the intake from the carb to the motor but what about the crankshaft seals or the case itself? The only way to know for sure that you don't have an air leak is to do a leak down test on the motor. This entails removing the intake and exhaust, sealing them off with a plate or plug of some sort that has an air valve, and applying either pressure or vacuum to the engine. If it won't hold pressure or vacuum, it has a leak. Some people make their own tools for this or they can be purchased. However, your dealer may offer this service for a reasonable charge so I would look into that first. Once you have verified the carb settings and condition, it may be time to make sure that air isn't entering through the crank seals or elsewhere.

Good luck!

Goofaroo · « **Reply #11 on:** December 18, 2011, 06:35:01 AM »

One more thing I might add: Is it possible to find out why it was in a wet cardboard box when you bought it? This is clearly a different scenario than the typical "ran when parked" routine.

ThomasD883 · « **Reply #12 on:** December 18, 2011, 06:36:23 AM »

I will have to check the crank seals, I did not reallise that could leak air. Makes sense though as the crankcase is the intake. Thanks again, I will hopefully have time this week to work on it. Learning something new all the time

ThomasD883 · « **Reply #13 on:** December 18, 2011, 06:42:21 AM »

I actually got it for free in the box, figured is have some fun putting it togethe kinda like a two stroke puzzle.

originally it was run without oil, piston lube as its oil injected, it trashed the piston. She got a new piston , bore and rings. Seals and all too but I'm pretty well betting that the crankcase seals are leaking air.

Goofaroo · « **Reply #14 on:** December 18, 2011, 07:35:30 AM »

Keep us posted. I hope you can get things going. Even if you could get it running a bit better like it is it would quickly destroy itself if it is sucking unwanted air into the case. Once everything is fixed, that bike should be effortless to start and very reliable.

ThomasD883 · « **Reply #15 on:** December 27, 2011, 03:24:35 PM »

Great thanks, i think i got the problem pegged. I made up some plugs , plates , and adapters to pressurize the crankcase and cylinder with regulated 5-7 psi and behold, the f'in right side crankcase seal was leaking air like it was supposed to do so. I'll be posting pic to add to the repair compendeum held here.

Might have another toy.

Goofaroo · « **Reply #16 on:** January 02, 2012, 08:59:39 AM »

I'm glad I could help. When the bike was run without oil it was hard on several things including the crank seals. Let us know how it turns out and DON'T FORGET PICS!

Duperdawg1 · « **Reply #17 on:** January 27, 2014, 11:35:04 AM »

Hey All,
I read this post and I believe I'm having the same problem with my sons 2003 JR 80.
Just had the top end and carb rebuilt at a local repair shop. The guys working on it couldn't track down the high idle problem, so I
Took the bike to the local Suzuki dealer and paid them run a diagnostic. They came up with a leaking crank seal on the stator side and a quote of $780 to repair!!! I politely declined and paid for the diagnostic.
Can the crank seals be replaced without splitting the case and major surgery to the bike.

Hunter 1 · « **Reply #18 on:** January 28, 2014, 08:38:29 AM »

I`m not sure if you will have to split the cases or not to change the seal. I have a Yamaha RD60 that I am restoring and the guys at 2strokeworld.com have been very helpful. The motors are very simple to work on and if you have a press you can change the seals.

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Author Topic: 2 Stroke suzuki JR80 tuning help (Read 17863 times)