Hard to Start

[russt]

My 1970 Suzuki T350 is getting very hard to start. It was running OK about 3 months ago. I changed the spark plugs but it does not help. I am not sure if I have an air issue or too much fuel. It acts like it wants to idle then it cuts right off with throttle or no throttle. Any suggestions?

[karl pa]

When you changed plugs,did you check it has good spark,did you check points?
Is it trouble at cold start or any start?
Does it start,how does it run?
If it doesn't want to idle, it could be blocked pilot (idle) circuit in carb.

[russt]

I put 2 new NGK B7HS plugs in this week. They seem to be sparking good. Its hard to start in all types of climates. The points are about a year old. They seem to be ok. When it does start(after many kicks), the right side fires good and smokes a lot and the left side fires fine for about 30 mins and then it sputters and cuts in and out with little to no smoke. I noticed that the carbs sweat a little around the bowl area. The battery is probably a year old but holds charge while riding.
All the lights work.

[jabcb]

3 months is long enough for modern ethanol gas to go bad. If the bike mostly sat unused for 3 months, first step should be fresh gas.


The condensers and/or coils might be problematic. Either could have an intermittent short that could start acting up after 30 minutes of heating.

The T250/T350/GT250 have a tendency to run on one cylinder if the battery is weak. You should fully charge the battery when sorting out the issues.

Also, you may find that you can start & run your T350 without a battery. NEVER DO THAT. The battery is the voltage regulator. You will burn out the lights if you run the bike without the battery.

The jets for the choke are in the bottom of the float bowls. Because of where they are located, it doesn’t take much crud in the carbs to have problems with those jets. These jets are not removable. Use a flashlight to see if they are clear. Needing mass quantities of kicks to start a cold motor is symptomatic of this issue.

Your bike has two pilot jets in series. Both are needed. The little pilot jet has a big hole & should be fine after ultrasonic cleaning. Which is good because they are NLA and are made from umobtainium. The big pilot jet has a tiny hole. Its a standard Mikuni jet & are easy to get. I replace them with new genuine Mikuni jets rather than fuss with trying to get them clean.

After sorting the ignition & carbs, the excessive smoking on one side may disappear. That’s what happened a few months ago when I throughly sorted a GT250. The excessive smoking was gone after new plugs, points, condensers, new pilot & main jets, and a good carb cleaning.


Other potential issues include a cruded up antique air filter, really low compression & shot crank seals. But if it hasn’t got easier to kick, and it ran fine a few months ago, then the above steps may get you back to a good running bike.

[russt]

I cleaned carbs and put fresh 93 octane fuel. Now its not starting. Im getting a good spark.. gas is getting to the left plug but the right plug is staying dry? Im not sure if it is a air issue or something else. I also charged the battery. It randomly makes a sputtering sound. . How air tight do the gas lines need to be? I see bubbles sometimes in the lines. How difficult is it to change the condenser? Thanks

[karl pa]

If it has good spark, I wouldn't worry about condenser now. I would think the carbs could still be blocked somewhere. These carbs have passages that can be hard to get clean, when I clean carbs I spray carb cleaner and air through each passage and make sure all passages are clear. sometimes it takes me several tries to get clear.
With air box removed, you can hold your hand over one carb, then the other while turning engine over,you should feel suction on hand when turning over, both should be about the same. This should show if you have large air leak issue.
The gas lines do get bubbles in, they only need to be tight enough to prevent gas from leaking out.

You also should double check float height, if your fuel level in carbs are low, could cause issues.

[jabcb]

If it used to start and now does nothing, you may have switched the sparkplug wires. Make sure operating the left points causes spark at the left sparkplug.

When you fill an empty float bowl with gas, the air has to go someplace. Air goes out the float bowl vent but some also goes up the fuel line & into the tank. Its normal to see bubbles in the fuel line when filling empty carbs.

You've been fussing with this problem, it may take a bunch of really hard kicks to get started for the first time.

[russt]

How much suction should I feel with the air box removed? It has acted like it wants to start but it cuts off immediately. I had to remove the new plugs and put the old ones back in.. that seems to help. With the new plugs it was not wanting to do any kind of idle?

Thanks for the post.. they are helping

[karl pa]

It should have a fair amount of suction, it wont suck your hand in though. You can also do a leak down test to check seals.
Are both cylinders getting fuel ?
If changing plugs made a difference, it could be a spark issue. Do you have a big blue spark ?

[alanr]

Loosen the carb bowl drain screws to make sure there is fuel in the bowl.check the fuel air screw is 1 1/2 turns out.

[Dave Robbo]

Keep to the basics to begin with its easy to start going off track. Remove the plugs and check compressions. Do you have the correct plugs in and are the gaps set correctly? Put a plug in each lead and touch to earth,ignition on then kick the engine over one kick should see a crisp blue spark across each plug providing points and condenser are good. If that lot is ok you move to fuel. If the engine is not starting both plugs should be wet not one as you say. If that's the case you need to look at the carb supplying that cylinder.

[tz375]

Sounds like two problems at least. If new plugs are an issue, throw them out. They may be copies and not made by NGK (assuming they are marked as NGK) there are lots of dud copies around on ebay.

Next, strip the carbs again. One trick I use is that when you think they are perfectly clean, grab a can of carb cleaner or WD40 and blow fluid through one drilling or jet and then repeat for the other side. That back to back comparison is hardly a measure of flow, but gives an easy indication of whether the flow is similar on both.

Double check the choke jet http://pinkpossum.com/GT750/carb/BS40carbs.htm" onclick="window.open(this.href);return false; that page is for CV crabs but the choke jet in the float bowl is common to most Mikunis of that era.

Then double check the choke circuits one drilling at a time - especially the long pickup tube.

After that check FUEL level. You will need a drain screw adapter and a length of clear plastic tube, but it's way more accurate than check the float level. That one replaces the bottom nut on a similar carb, yours is probably different but the principle is the same.

You might want to check the airbox and filter for nests and nuts and the same with the exhaust baffles.

[russt]

After cleaning carbs and running a feeler gauge over the points, it finally started. So far it is easy to start, the right side is running great BUT the left side is either doing nothing, popping or backfiring. I can see the backfire flame thru the clear tubing from the left carb.. My points gap is .011. its hard to adjust the points because one of the screw heads is getting worn out and is not turning with a flat head..

[joethebike]

Forget about the adjusting screws on the points and replace them with allen key headed screws then you will never have any more problems with rounded screw slots. I bought allen head screws from a supplier specialising in all types of nuts, bolts and screws, just take along a sample of the original screws to match thread pitch.

[karl pa]

running a feeler gauge over the points,

I would try electric contact cleaner, and pull a piece of paper through points. It sounds like the points may have some oxidation on them, preventing good contact, and sparking at the wrong time, throwing timing off causing popping and backfire.