Suzuki 2 Strokes

My 1970 T350 is brilliant but it always got all moody just when the fun should start around 4500rpm felt like it was missing, basically just bogs down. so I changed the plugs..then wow what a difference wheelies goes like a bat out of hell...for about 5 miles then back to rock bottom...change the plugs same again etc etc.
Any ideas of where to start..have you had a similar problem?
Any advice much appreciated

It is very possible that the jetting is rich. It's also possible that it needs hotter plugs to burn off the soot.

When unleaded became popular the oil companies issued all sorts of technical comments that suggested the need to run hotter plugs because unleaded tends to leave more carbon on the plug tip.

We find with our race bikes that we use D8 plugs with unleaded and D10 with leaded race gas. With the hot D8 it is still hard to keep them clean if we are not running absolutely flat out.

If you use B8 for example, you could try a B7.

T350 use #7 heat range. Check gap.

When it rock bottoms do you think it fouled a plug?


Here is the hit list

Check carb: pilot jet, main jet, needle jet ,jet needle, jet clip pos, float level. leaky float, air filter. Verify jets are Mikuni brand (sometime people use Keyster kits and ketster mixes old T350 carb part with later) and jets correct size per stock. Make sure they are OK not plugged, corroded or warn. Verify pilot air screw.

Does gas leak out of carbs? Put it on prime to see if it does, bike setting level, and if so maybe new float valve or at least float valve needle or float has hole or not set at correct level

Check spark (nice blue snap? fresh points (OEM best), gapped and timing set, Measure condenser, make sure it’s well grounded - not loose or just replace with OEM. Check Plug cap resistance. Ohm coils primary and secondary.

Verify oil pump setting

Does it smoke heavy out exhuast either side/both side and smell like gear oil?

My guess it's one or more of the above



If all well above

do compression test look for balanced compression bewteen cycls.

Does it rev up erratically when idling?

I had a problem once with the choke linkage. One of the plungers would not close completely when the choke was turned off.

It's getting annoying now...Removed the carbs cleaned everything that could be cleaned including the carb bodies, replaced the choke mech. You can rev the nuts off it on the centre stand, in the lower gears it rev further than the higher, but it just doesn't seem to want to go. try and accelerate down the bypass and sure as eggs are eggs it just bogs at 4000rpm it will occasionally rev higher but it wont pull. I removed the plugs and changed them it went like a Banshee but then very quickly went all sulky on me...I had a Wife like that...

Working on the tried and trusted mechanics maxim that 99% of all Fuelling faults are actually electrical..(the reverse is also true).
I shall have a looksee at the points /condensers.
Cheers
Bonnietiler

What is the sound and feeling when it won't deliver power?
spluttering.....rich?
bwoooah from airbox....lean?
Does it start hot and cold easily, idle well nice and slow? if so, crank seals not the obvious candidate fault
It is that it won't rev, or that it won't accept throttle? not the same. Can you redline it in 2nd when riding? 3rd? or is it that it won't accept half throttle or more without bogging down?
Good luck with the maddening thing!
Mike

I suppose more of a spluttering but it actually loses power when trying to accelerate, revs to about 5000 in 1st then progressively less in each gear. on the side sidestand and in neutral it will rev to the red line and beyond!
Ticks over like a bloodhound lapping milk starts very easily interestingly it does seen to leave quite an oil smoke trail from the exhausts when its trying to maintain 4000 rpm in top!

Now you may be getting somewhere. Sounds as it may be too rich, as your description sounds as it is loading up and 4-stroking as you get deeper into the throttle. It will smoke heavily (as it isn't firing every revolution, thus not burning the oil, so it has more to mioove when it does finally fire). It will also run progressively worse as the engine warms up.

I would check that your chokes (enrichment circuit) are in good condition - closing fully and plunger seals ok. If that's OK, try dropping the jet needles down a notch, and see if the condition improves.

Just cleaning carb parts is trivial; jets can be bad, wrong or not set properly, even if they are clean

Should use my first reply as a check list and with careful scrutiny.

Until you approach it this way you are just going to keep guessing missing potential fundamental mistakes. You need to be sure of what it’s not and start honing in on what it is.

You should check all subsystems (Fuel, Ignition, Injection, Mechanical) for may be more than one may need servicing.

Good news, These old bikes have proven they can work very well and are reliable and comparably they are simple to work on

and this one too ->

Vintageman wrote:Does it smoke heavy out exhaust either side/both side and smell like gear oil?

for the center seals on these specific models have a track record of getting stiff and then let pushed (center bearing gets oil from gear case) gear case oil into piston crankcase area. There are possible patch fixes for this or replacement of seals.


Good luck