Suzuki TS50 Running bad. Few questions...

[jgtynan]

Hi, Im new to this forum. I ride a Honda xlx250r enduro which I love. I have just bought a Suzuki TS50 offroad/moped type thing for my younger brother to learn the basics of offroading on. It needed a clean of the carb and plug, and some fresh fuel and she fired up (separate oil tank-working oil pump). But she runs fine when freshly started, but when she gets warm (4-5mins) she loses almost all power. She will just about rev up in neutral with a lot of feathering of the throttle, but put her in gear and she just wont pull. I have tried the needle clip in all positions and although the characteristics of the engine change, it still bogs once its warm. The piston and cylinder look good, but i think rings might be due for a change as theres evidence of blowby past the piston.

Would the rings cause these problems??

Its an iron sleeve cylinder, I wont need to rebore this will I?

Does anyone have any experience of these little Suzies? I would be glad of some data on the engine-
I.e; Carb needle stock position,
air screw setting,
compression range for this sort of 50cc 2stroke engine,
What the end gap measurement should be for the piston rings.

Sorry its so long, :yikes: but it might help diagnosis.
Greg

 

[jgtynan]

Oh, forgot to mention, It wont idle on its own either. If you blip the throttle itll 'idle' while the revs are dropping then hold a slow idle for 2-3 secs and die. Idle screw is screwed right IN. I have set the air screw to where the engine is 'happiest'.
Anyone got any ideas? Anyone got any technical details on the carb settings etc?? plz
Thanks
Greg

 

[SHSPVR]

You didn't what year this is
When it cold then in gear will she pull after 15/30 sec warm up?.
PSI compression usedly if less then 55 then it need be rebiuld but as rule 2-stroke need be maintaining around 80 psi.
Are rings free from the piston
Carb may need more cleaning
Weak spark it may need new set of points

 

[jgtynan]

thanks for the reply. I think its an '89-'90 year. TS50X (air cooled). It has CDI, so points shouldnt be an issue (correct me if im wrong-might help lol). The piston rings are free but dont look like theres much of them left. Im getting a cylinder pressure of just under 65 PSI. After 15-30 seconds from cold, she pulls quite well until shes ran for about 4 minutes, then she loses all power, and as long as you keep playing with the throttle she will stay running for ages. Spark is very healthy and willing. I have ordered a new piston kit anyway, theyre cheap enough. You dont reckon the cylinder would have worn too do you? How many pistons can you go through on an iron bore before you need to re-bore it?
Thanks
Greg

 

[SHSPVR]

Cast iron cylinder do ware you cant really tell in you have quick few light pass honed done then it eazy to see.
And from the sound of it that your problem soon it warm up it lossing more PSI if that is cold compression test of about 65 PSI so it may be worn out rings and piston.

The best way is to have cylinder measurement see it still with in 41.00mm Bore but not then 41.20mm over stock if is stock.
Check the Cylinder and Piston clearance with reg old feeler gauge it be with end .040mm to .070mm
New ring gap should be with end .15 to .35mm if it more the .45mm it need be bore.

 

[jgtynan]

Thats the info i was looking for. Thanks, The ring end gaps on the old piston are definately over what you have specified, but i thing thats down to the rings being so worn. 65PSI is from cold. When I go to pick up the piston, Ill take the barrel with me so the guy can measure it for me. then Ill have a better idea. Thanks for the help. I dont suppose you know the stock carb settings do you?
Thanks
Greg

 

[jgtynan]

New oversize piston and rebore, new plug and its running well. Not bad power for a 50cc. But when I leave it idling for a couple of minutes once warm it bogs badly (only under load), if you ride it gently it sorts itself out and regains its power. what could this be?thanks
Greg

 

[SHSPVR]

Make dbl sure that put the rings on rigth.
Usedly there mark one of the ring like a letter or number or both or small dot that usely the top ring and the marking need be facing up.
Now, note the forward direction of your piston if it has an arrow stamped on it which need be pointing to the Exhaust Port.
Check the Spark Plug make sure that it not run rich or lean which could a few things it may need jet down or up did rem to put the carb needle back where it was at 3 slot? or float not work rigth where it get much fuel in bowl.

 

[jgtynan]

Piston and rings fitted correctly, plug showing evidence of a little richness but i cant figure out whats causing it. Tried to set the float level but not sure what it should be at. My guess is that the float is to blame. Needle clip (i think) is on #3. A hell of a lot more compression now, it used to bump with no hassle in 2nd gear. Now it barely moves in 3rd.
Cheers
greg

 

[SHSPVR]

Frist try Needle clip on #5 or very top slot is there any diff?.
Fuel level should be about 1/2 full or less then 3/4 in the bowl
Sorry I don't have any spec on carb.
How ever if can fig out which mikuni model you have in most cases you can cross ref it with newer bike.
It may the Mikuni VM12 which should eazy after all JR 50 has the same carb
With the carb upside down and the float bowl off measure the float height.
It should be within .90 - 1.00 inch

 

[jgtynan]

Will double check fuel level, but i think its as near as. It is a VM12 carb. Tried needle in #2, #3, #4, #5 and #6.

#2, makes the bike pretty un-ridable, It will barely idle too. No power to pull anywhere in the rev range.

#3, rideable but you need to work to get power. Will only ride if you ride at full throttle. When engine is cold, it runs perfect.

#4, Best setting. Idles ok. When COLD the engine runs perfect, once warm then it will need really high revs and a little push to move off in first, and you need to take it to the end of the revs in 1st before going to 2nd. The bike struggles at about 2/3 throttle, anything above is ok. sometimes anything below 1/2 throtle will be ok too. Plug is a nice tan color too.

#5 & #6- too rich.

I have installed a K&N filter and a better flowing exhaust. I have changed the main jet from 85 to 87.5. I havent changed the the pilot jet - guy in the shop said pilot jet wont matter but i think it is running lean at lower throttle??? Main jet seems ok as the plug is a nice tan colcour after riding at high revs. What do you think?? :bang:

 

[SHSPVR]

It possable that jet a tab to small so it can hurt try one or two size bigger but idle jet controls the idle and on up to quarter throttle.

 

[jgtynan]

Fair enough. I'll order a bigger main (again), and I have already ordered a 'next step up' pilot jet. That should be here tomorrow. Hopefully I can put them both in at the same time.
Would a K&N cone filter and a more flowey exhaust make that much of an increase in the amount of intake air to need 2 or 3 sizes bigger on the main jet? :think: LOL my little bro should see a bit of an increase in power from his beasty 50 :) :ride:
Cheers
Greg

 

[SHSPVR]

Usely when you buy a better after market Expansion Pipe & Silencer they need be jetted down.
As for K&N filter it just more free flowing filter that dosen't change the way the carb works which alway be same amount of intake air only a bigger bore will increase intake air charge.
Read this to get a better under stand on how they work
http://www.motorcycle.com/how-to/ho...ambers-work-and-why-you-should-care-3423.html

By the way did check your reeds to sure that sitting flat?.