Help in setting up a suzuki ts50 70 big bore kit

[trh71]

Hi all

I picked up a ts50 for my lad, but it struggled to do 30? It turned out it had been "messed" with. Some idiot had been in with a dremel, inlet, outlet, ports underneath and not tidy!
So I've picked up a good 2nd hand 70cc barrel & piston and also a Dep exhaust.
I'm running a K&N type air filter, the carb is 15mm (is this standard?)
It had 95 main and 12.5 pilot jets in and a hotter plug (7).
It wouldn't kick off, but I bumped it off and it ran but wouldn't tick over.
I've got a 17.5 pilot and 115 main in, it kicks with a bit of throttle, but wont tick over under 3k
Am I right or am I going too big, or do I still need bigger??
The other thing is oil mixture via oil pump
Its doing my head in

[DMCpro]

Do you have the standard air box
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Honda CB-1, TS125X
VW Golf Estate

[trh71]

Yes I still have it, but thought a K&N cone filter would be better?

[smegballs]

[trh71]

Sounds like a plan!
In your opinion, is 115+ main jet big for a 70cc?
Its been getting better the bigger I go

[smegballs]

[trh71]

std is 62.5 I think, but im not sure if its a std carb, it had a 95 in with the messed around with 50 barrel, std air box and derestricted std exhaust

[trh71]

std pilot jet is 17.5 but it had a 12.5 in?

[stevo as b4]

If you can get the specs for the std carb and then verify that's what you have on the bike, I would start about 3-4sizes up on the mainjet from the std 50cc setting. A 70cc big bore kit should not need more than around 4 sizes up on the mainjet, and changing the airfilter would probably need only 1-2sizes bigger on the MJ.

It's normally always the midrange fueling that is buggered up when fitting a different filter or sometimes a different exhaust.

My gut feeling is that if your running a std car, that your main jet is way to big at the moment.

[smegballs]

Might want to take a read of this.

https://www.iwt.com.au/mikunicarb.htm

Apparently some mikuni jets are measured in volume of fuel delivered.

So very roughly speaking....

70/50 = 1.4

A 70cc is going to need 140% more fuel by mass than a 50cc, let's ignore temp changes and shit for now.

62.5*1.4 = 87.5

What complicates things is stuff like derestricted pipes, and air filters and shit which throws all the original estimations way off. I'm by no means a two-stroke tuner, that just to try and get you a rough idea of where you're at.

Gonna be trial and error to get it running well. Played with the needle jet position too?

To be fair my mates, TS50 never idled without revving its tits off, and was generally pretty shite. My DT50 was the far superior machine

Good luck.

[trh71]

Thanks
Well going off that, without the K&N on, as it was (50cc), with the Dep exhaust on, it was running a 95 main jet, so 95X1.4=133 which makes sense, as it has been getting better the bigger I go.
What about the pilot jet, what dose it do? Tick over?
The only other thing is OIL, if I'm putting this much more fuel in I better turn the oil pump up!
Just taken it for a run, 42mph, it ran well, plug colour good.
I'll get some bigger jets tomorrow and see if that sorts out the starting and tick over probs.

[smegballs]

https://www.iwt.com.au/images/effects3.gif

[trh71]

How dose this plug look to you? It's reddish in colour.
This plug was new, had it in top gear up slight hill, clutch in and hit the kill switch
This is what I got. Too hot?
Still low on power low revs, bigger pilot jet?
Would that make it leaner still?
Going to get some more jets tomorrow, but thought I'd throw this in

[bladerunner]

I'd probably try a bigger main jet and work your way down. Hard to say from the pic tbh but deffo not looking rich. What's it reving to now?
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[trh71]

I'm already up to a 115 main 17.5 pilot
It redlines in neutral and pulls about 8k in gear

[trh71]

The other thing is, I'm still running oil via the oil pump, I have turned it up a bit, could I be short of oil?

[trh71]

As I have it now;
Dep expansion pipe and std (ish) can
K&N type filter
115 main
17.5 pilot
needle down 1 notch
Oh and oil pump turned up a bit
It starts with 1\8 throttle and revs well up to 10k
Take it down the road, you get it up to 7k in top (35-40mph) and it starts popping, back through the carb I think
Any ideas??
Its impossible to do plug chops like this

[bladerunner]

Just a roadside bodge idea if you don't have different jets to hand but if you turn the choke on does it make any difference to when it starts misbehaving? I would be aiming for it to be making good power in the 8 k rpm range ideally. If it makes no difference and rolling off the throttle without the choke on does not help either....then suspect plug and/ or you can't get enough exhaust gas out of the cylinder fast enough ( not good!) the std front pipe is a serious restriction on the ts50 so you've already improved on that...as a long shot tail pipe may be causing too much back pressure but I'd expect that to need to be quite badly blocked ...try a run without to see!

Is your big bore one with the extra intake ports (crank case induction) as some doand some don't. The ones that do with a big one exhaust are capable of 50-55 mph on the flat and 60+ downhill if geared up a little.
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[trh71]

I'll try the choke method tonight.
As for the end can, that's been cut up burnt out, a few more holes put through and welded back together. Why would it start popping when riding if it revs ok in neutral?
The barrel looked pretty much the same apart from being cast iron instead of alloy.
And plug was new

[bladerunner]

When your reving it in neutral there is no load on the engine...it could be ignition timing or the such but doubt it if it's the Cdi version as they usually respond well as std
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[trh71]

OK its really doing my head in now!!
I must've tried every combination of main/pilot jet and needle height, but its still popping back through the carb. Worse lower I go.
It runs best at 115 main 17.5 pilot, needle clip down one notch. But it still pops at 7-8k??
What the hell is up?

[smegballs]

[bladerunner]

Nowt wrong with tuning 2 strokes and the little ts50 is a good base line for just bolt on bits like your dt 50 was. They should and are designed to make 3 times the power they do when restricted to moped specs. Granted you'll be fitting a new piston every 3 months to keep them in good tune but should no be because of blowing up oe seizing so no rebore needed if done when top speed drops from 55-60 to 45 mph!
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[trh71]

I'm a little red faced this morning
I pulled it in bits again last night, how I never noticed it when I put it on, it's in need of a rebore and oversized piston, well sloppy!
So that's where all my pressure has been going and that's why it's been popping back through the carb! No bloody wonder I couldn't get it tuned in!! What a plonker I feel
I'll let you know how I get on

[bladerunner]

Ah well at least a good reason for the problems. Be interested in seeing how you get on after the refresh!
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's