1971 T350 Wont run over 4000 in top continues

[bonnietiler]

So I've been away for a while but I'm slowly rebuilding the bike although it's in great original (non running) condition.
Recently NOS coil..NOS condensers...NOS contact breakers, I didn't expect this to have any dramatic effect as I'm fairly certain the problem is Fuel
The bike is now timed beautifully and starts almost instantly.
I have stripped and THOROUGHLY cleaned the carbs replaced anything internally still the problem persists
It runs to higher revs the lower the gear so excellent in first..then less and less so that in top it struggles to pull 60mph feels like its running out of puff
It does leave a fairly impressive white smoke trail which leads me to think its overfuelling
I have just had a good looksee at the carbs and they are stamped Mikuni no surprise.. but on the flange where the fixing bolts are they are stamped (Leftside) T85 30 and the right side T86 30.
I'm now at the stage of wondering if I have the correct carbs on my bike..is that correct...that might be 186 30 or even 786 30 its difficult to tell...but its the 30 that has me thinking I'm sure my carbs are 32..Is it just a casting number..or am I trying to tune incorrect carbies?

[Suzukidave]

Does it have stock gearing ?

[joethebike]

Suspect your crankshaft seals. That was the answer to my 350s similar problems after endlessly playing around with carburettor settings.

[Vintageman]

impressive white smoke trail

white?

I have had a few old T305/T350/GT250 and the center seal is usually bad. It doesn't leak crankcase air, just gear oil (opposite direction) but that is usually blue based on color of gear oil burning.

For me if seals are leaking air somewhat hard to get steady idle where the leak of air is more sensitive since carb slide are closed. WOT may be masked out. If seal is wasted you can feel less suction when hand over carb mouth.

Leak down test (of some kind)

Why do you think carbs may be wrong? Do you have pics of bike? Did you verify ALL jets and needles etc. Are the all Mikuni or after market?

Did you check timing using TCD method or the flywheel marks (Key Way spun?)

Actually I am not sure I know what white smoke is on air cooled bike. Just some ideas for you

[GT750Battleship]

Hi,back to the carbruettor,& look at the jetting,are you using the pump alone for the oil, ?
never add two stroke to the fuel tank,makes things very lean !
Failure of crankcase seals will make it smoke like crazy on one or both sides as it will be burning gear oil ! Have you done a compression test or a leak down test ? This will give you a good understanding about what's going wrong +1 with Vintageman's comments
Regards,
Roger
Suzuki GT750A

[Coyote]

Actually I am not sure I know what white smoke is on air cooled bike.

Annoying as hell.

[bonnietiler]

All internal parts to carbs are Genuine Mikuni all in good shape.
Carbs have the markings 30 which leads me to think that they may be 30mm carbs?
Bike only smokes when attempting to get a high top speed in top or 5th.
other than that absolutely normal, it starts very easily and ticks over slightly high..can't seem to get it to tickover at less than 1700rpm.
One day I changed the plugs and it ran like a missile for about 2 miles then back to normal.
Can't seem to find anything to fix anymore...other than stripping it right down..seems a shame it being in such good condition.

[Alan H]

As it seems to be causing you lots of tears and anguish, I'll take it off you and won't even charge for coming to fetch it.
Can't be fairer than that.

In the meantime, (I offer this to anyone with an early model bike) I have an electronic copy of an early (1972) service manual for all models. If you PM me your email address, I'll send a copy FOC.
Can't be fairer than that.

High irregular tickover is usually either leaky inlet rubbers - spray some carb cleaner around them and if the revs rise, thare's the leak, or the pilot air screws need adjusting/or slow running jets partially blocked.
Remember that the book settings are for new carbs back in the day, not 40+ year old carbs that have been up and down the street a squillion times.
Fair? in yer dreams - this is an old bike with character - or just bloody minded. You pick!!

[jabcb]

Based on the tank & cylinder head, that’s a 1970 T350.

The carb part numbers are left: 13202-18630 & right: 13201-18630

I looked at my carbs, which are numbered with 186 appearing above 30.
That’s the second part of the carb part number, 18630.

[grumpy56]

THAT is a nice 3 fitty!!!

[GT750Battleship]

Hi,I just had a thought...the earlier twins T20 & the like,can suffer from heat transference from the engine to the carbs by way of the spacer block between engine & carburettors which fail due to age.Over many years of operation this distorts the carb bodies & the slides don't operate as well as they should ?
Cheers,
Roger

[Suzukidave]

Its a bit of a setup but a leak down test would be good to do . This would answer if there is any seal or vacuum leak problem .

[Vintageman]

I agree that the early T350. I think that one had the ports similar to the earlier T305. Now he is something that confused me. The first t350 (69) had same jetting as the T305. Then jetting changed.

I have had both jettings and both work well on either T305 or later T350. Mixing them up in a carb is bad . I would imagine the carb had all original parts. But any chance you recall the jet #s Needle#, clip pos, Needle e Jet #, pilot and Main jet #. was it a round or hex main?

That bike is so nice you should pull the engine out and give her a good look see if you at wits end. That bike is beautiful

If it can't tick less than 1700 rpm pilot circuit plugged, bent idle adjusting rod or vacuum leak (seals).
When you pull the plugs after running poopy what color are they? (Pic?)

White smoke huh, both pipes? Plugged exhaust? White smoke is from crap inside pipes burning up?

Tell me again how you check ignition timing.