*Parts Compatibility - TBS 1998

[Biiim]

Atom, which of these are you referencing

Like it looks like there are two vacuum hoses?

That looks like the likely place it goes. It’s possible that all vacuum lines and such need to be connected for it to run properly.

should I try attaching the tank and hoses properly to see if I can get it to idle right ? Also I broke the fuel filter -the little plastic one that goes on the fuel line

 

[sikatri]

Like it looks like there are two vacuum hoses?

should I try attaching the tank and hoses properly to see if I can get it to idle right ? Also I broke the fuel filter -the little plastic one that goes on the fuel line

I would get the setup to be complete even if temporarily.

 

[JCooper]

This oily hose going down and to the right from the elbow is the crankcase vent. It should connect to a fitting on the bottom of the air filter box, which you don't have. You'll need to route it somewhere else. Run the hose up, never down, so oil will drain back, and put a breather filter on it.

I made an oil separator from a separator for an air line and mounted it on the frame tube behind the pod filters.



This fitting is not stock. This elbow is coolant from the water pump to the cylinder block. There is no fitting there and nothing connects there on a stock TBS.

These two look like the bowl vents. They should connect to the two "T" fittings that are between the carbs on the side closest to the cylinders. (The ones away from the cylinders are fuel in.) The free ends get tucked up under the tank where they can breath without having the wind blowing on them.

This little nipple on the bottom of each float bowl is the bowl drain. The screw just above it is a needle valve that opens the drain.

Here is a diagram of the cooling system for reference.



There is no in-line fuel filter and adding one often causes more problems than it cures. There is a "duck bill" screen in the "T" fitting at the carbs where the fuel tank connects. It's the sort of white plastic bit stuffed into the fitting.




HTH

 

[JCooper]

Just one more thing: if the carbs have not been jetted for the pod filters it will run like crap at any throttle setting much above idle...

 

[atomsplitter]

The problem to get it to idle with fuel is the next hurdle. The starter fluid doesn't need any metering, but your carbs do. The air is causing the fuel mix to be too lean to run the engine. There are a couple ways to start but the choke is a starting point. The choke cuts air to the engine so it runs very rich when cold. Make sure the choke is pulled to cut as much air as possible at idle. Once the engine warms up the idle speed will increase and the choke can be turned off.

There is also the possibility the idle mix is now way too lean as well. The pilot air/fuel screws are usually on the bottom of the carb. Did you clean that when you were cleaning the carbs, i.e. pull the screw out and run cleaner thru those passages? Here's a short video on idle mix screw adjustment:

Here's what should be your carburetors: Item 10 is the pilot screw, and by the looks of the drawing it may be metering fuel. In either case the plug that covers it needs removed so you can access the screw to adjust it. Whenever you are going to seat (close) the screw DO NOT go past where it stops, otherwise you will ruin your carb.


Here is a pic of what the rebuild kit should look like for the 900 Sport engine: The pilots look like fuel metering pilots and the tips are VERY fragile. The drill bit is to remove the plug cap over the pilot screw. The spring maintains tension on the screw threads so it remains where you set it under vibration loads. Assuming it's metering fuel the further OUT it's screwed the MORE fuel at idle, the further IN it's screwed leans the mix. With the screw seated all fuel is shut off and the engine won't run at idle. The three rubber plugs are to blank the nipples on the intake manifolds, check that yours aren't cracked and leaking air.

View: https://youtu.be/zm5mB3R8Ucw

 

[JCooper]

Set the idle mixture screws at 2-1/2 turns out from lightly seated for starters. Install spring, o-ring and washer on the idle screws, in that order.

These carbs do not have proper "chokes". They have cold enrichment valves. These valves do two things. First they introduce extra fuel, and second, they allow a little extra air around the throttle plates. The fuel added is in a higher proportion than the air, so the mixture is enriched, and the extra air increases the idle speed.

The pilot (low speed) jets and the associated passageways in the carbs are susceptible to clogging on engines that have sat for long periods of time. Cleaning them is vital to getting the bike to idle and accelerate properly. Don't use metal tools to clean the holes in the jets; you'll upset the flow rates. Also, the air bleeds in the sides of the pilot jets need to be clear.

With pod filters, you should probably have #42 pilots and #145 or #150 main jets. A 0.5mm shim under the needle might help, too, but worry about that (hesitation off idle) later.

This is a used engine, right? Do you know what model bike it came from? The extra coolant nipple makes me think it may have come from a different series, and may have different cams, in which case the jetting will be different.

 

[JCooper]

Put some heat shrink or liquid electrical tape on the bare wire on the oil pressure sensor.

 

[sikatri]

A good point on the cams and jets @JCooper.

 

[atomsplitter]

A good point on the cams and jets @JCooper.

+1

 

[Biiim]

Set the idle mixture screws at 2-1/2 turns out from lightly seated for starters. Install spring, o-ring and washer on the idle screws, in that order.

These carbs do not have proper "chokes". They have cold enrichment valves. These valves do two things. First they introduce extra fuel, and second, they allow a little extra air around the throttle plates. The fuel added is in a higher proportion than the air, so the mixture is enriched, and the extra air increases the idle speed.

The pilot (low speed) jets and the associated passageways in the carbs are susceptible to clogging on engines that have sat for long periods of time. Cleaning them is vital to getting the bike to idle and accelerate properly. Don't use metal tools to clean the holes in the jets; you'll upset the flow rates. Also, the air bleeds in the sides of the pilot jets need to be clear.

With pod filters, you should probably have #42 pilots and #145 or #150 main jets. A 0.5mm shim under the needle might help, too, but worry about that (hesitation off idle) later.

This is a used engine, right? Do you know what model bike it came from? The extra coolant nipple makes me think it may have come from a different series, and may have different cams, in which case the jetting will be different.

Correct it is a legend Tt 98’ engine 5 speed the carbs (including pod filters) where jetted for the original tbs 98 engine which is a 6 speed.

 

[JCooper]

Correct it is a legend Tt 98’ engine 5 speed the carbs (including pod filters) where jetted for the original tbs 98 engine which is a 6 speed.

OK, jetting between those two is the same, but you have the pod filters. Do you know where they came from? If they came from the TBS, then use the carbs from the TBS.

 

[Biiim]

OK, jetting between those two is the same, but you have the pod filters. Do you know where they came from? If they came from the TBS, then use the carbs from the TBS.

I worded that poorly. I swapped the tbs engine with a legend TT. The pod filters and carbs where on the tbs before swapping the engine.

 

[sikatri]

Mixed me up. Are these the carburetors that came with the “new” engine?

 

[atomsplitter]

Whatever carbs are on the engine you are trying to run have a problem feeding adequate mix to the combustion chambers from your description. Let's tackle this with first things first approach. At idle the CV slides aren't part of the equation, it's the idle circuit, which is the idle mix screw and the 'choke' porting fuel and air. You stated you had cleaned the carbs, did that include pulling the idle mix screws and spraying carb cleaner into the hole? That would be the item #10 in the above diagram.

 

[Biiim]

Set the idle mixture screws at 2-1/2 turns out from lightly seated for starters. Install spring, o-ring and washer on the idle screws, in that order.

These carbs do not have proper "chokes". They have cold enrichment valves. These valves do two things. First they introduce extra fuel, and second, they allow a little extra air around the throttle plates. The fuel added is in a higher proportion than the air, so the mixture is enriched, and the extra air increases the idle speed.

The pilot (low speed) jets and the associated passageways in the carbs are susceptible to clogging on engines that have sat for long periods of time. Cleaning them is vital to getting the bike to idle and accelerate properly. Don't use metal tools to clean the holes in the jets; you'll upset the flow rates. Also, the air bleeds in the sides of the pilot jets need to be clear.

With pod filters, you should probably have #42 pilots and #145 or #150 main jets. A 0.5mm shim under the needle might help, too, but worry about that (hesitation off idle) later.

This is a used engine, right? Do you know what model bike it came from? The extra coolant nipple makes me think it may have come from a different series, and may have different cams, in which case the jetting will be different.

I turned each idle mixture screw ( #10 on the diagram ) 2 & 1/2 turns out. They were seated pretty snug. I wonder if I ruined them. I did clean them. My understanding is that I should also adjust the pilot jets? I can order new washers for the idle jet. I find it interesting that when idling and twisting the throttle it cuts out. On top of that i tried turning to over to many times and now the battery is at 6v not 12v where it should be.

 

[Biiim]

Mixed me up. Are these the carburetors that came with the “new” engine?

No. sorry bout that confusion

 

[Biiim]

Whatever carbs are on the engine you are trying to run have a problem feeding adequate mix to the combustion chambers from your description. Let's tackle this with first things first approach. At idle the CV slides aren't part of the equation, it's the idle circuit, which is the idle mix screw and the 'choke' porting fuel and air. You stated you had cleaned the carbs, did that include pulling the idle mix screws and spraying carb cleaner into the hole? That would be the item #10 in the above diagram.

Yes

 

[atomsplitter]

I turned each idle mixture screw ( #10 on the diagram ) 2 & 1/2 turns out. They were seated pretty snug. I wonder if I ruined them. I did clean them. My understanding is that I should also adjust the pilot jets? I can order new washers for the idle jet. I find it interesting that when idling and twisting the throttle it cuts out. On top of that i tried turning to over to many times and now the battery is at 6v not 12v where it should be.

Could be bad news. Pull the idle mix screws and see if the tips are undamaged. If either tip is broken off your carb body is ruined and you'll need a new carb body. Happened to me on a used Yamaha XS1100 years ago, I had to buy a full 4 carb set. Luckily you have some spares. As to the battery, put it on a charger and see if it can get to 13.2 volts off the charger. If so, good, if not, new battery time.

BTW here's that old Yamaha:

 

[JCooper]

Forget everything anyone, including me, said about carbs. You need the carbs (or at least the jets) from the TBS if you're using the pods from the TBS.

 

[JCooper]

Forget everything anyone, including me, said about carbs. You need the carbs (or at least the jets) from the TBS if you're using the pods from the TBS.

The pod filters and carbs where on the tbs before swapping the engine.

Never mind. I misread post 132.