2003 yamaha F90TLRB carb rebuild

[merk175]

I've ordered rebuild kits for carbs on my 90 hp 4 stroke. I have a service manual but cannot find any info on how to rebuild the carbs..... Can anyone direct me to where I can find some info? thanks

Glenn

 

[99yam40]

Re: 2003 yamaha F90TLRB carb rebuild

Carbs are carbs whether on a OB, auto, or other gas motor. you take them apart and clean them and then put back together, making sure you do not mix up the parts and pay attention on how you took them apart.
The tricky part is setting them after reinstalling. I believe the 4 strokes probably need to synced with multichannel manometer , but your service manual should tell you all of that.

You might check u tube to see if they have anything on it

I see you finally found your model # and it went from 2005 to 2003 motor

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

I understand how to take carbs apart and clean them. I was looking for info such as float height etc... or does it even need to be adjusted? As for the model number, I was told the engine was a 2004.
when I gave the model number/serial number to a dealer trying to find a service manual, they told me the model number doesn't fall in 2004 and must be a 2005.....

Here is the info...you tell me what it is:

F90TLRB

61P L 1002808
Q

 

[99yam40]

Re: 2003 yamaha F90TLRB carb rebuild

good to see you posted the model # this time, and it shows to be a 2003.
Yamaha service manuals show all specs for motor, I do not understand what manual you have.
Maybe a owners manual?

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

I bought carb rebuild kits, cleaned them all, and rebuilt. Reinstalled carbs and now the engine idles great but.....I still have a hesitation when I accelerate. Also "COUGHS" when I try to accelerate hard. Still seems to be lean when I accelerate. Any ideas???

 

[yamatech43]

Re: 2003 yamaha F90TLRB carb rebuild

Buy a SERVICE manual...owner's manual is useless for technical info....yes the float height DOES need to be set....the dealer will be happy to order a SERVICE manual for you. How did you clean the carb's?

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

Buy a SERVICE manual...owner's manual is useless for technical info....yes the float height DOES need to be set....the dealer will be happy to order a SERVICE manual for you. How did you clean the carb's?

I have the service manual. I never said I was using an owners manual......I don't have the owners manual for this engine.

How did i clean them? I removed all carbs, disassembled everything, soaked them in laquer thinnner, then blew out all passages and parts with compressed air. Once completely clean and dry, I reassembled them using new carb rebuild kits complete with all gaskets, needle, seat and new float. I set the float levels up as per the service manual and re-installed the carbs on the engine. the only thing I did not do was to sync the carbs but I was careful not to change the set screws so I assume they are in sync. I don't have the tool to sync the carbs.

 

[multimech]

Re: 2003 yamaha F90TLRB carb rebuild

"I don't have the tool to sync the carbs." Here is the root of your problem. WHENEVER four stroke carbs are rebuilt, they need to be "synched" as in making sure the vacuums on all intake ports are near the same. Take it to a dealer and have it done or get a manometer for yourself. My next question is, have you done a leakdown check on the cylinders?

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

after rebuilding carbs and changing plugs, the engine has been running very well. a slight hesitation on hard accel from idle but other than that...no issues until yesterday. Was out fishing and ran from one spot to another and when I slowed down to idle, out of no where the engine will not idle at all. anything below 1100 rpm and it stalls. At WOT, it seems to be running fine. Once i got home, I idled it at about 1200 rpm and pulled one plug wire off at a time. When I pulled the #3 wire off, there was no change in the way it was running so the misfire is obviously there. I switched the coils, no change...still misfired on #3 cylinder. any ideas on what to look at next??? thanks.

Glenn

 

[99yam40]

Re: 2003 yamaha F90TLRB carb rebuild

I would think it is carb related if it will not idle at all.
Even with one cylinder not firing properly it should idle ,just an opinion.

Do a leak down test on all cylinders
Check spark with a spark tester, you can pick one up at any auto parts store.
Check timing to make sure it is in spec the at different RPMs
Check fuel pump for leaking diaphragm

If all is good, then you have carb problems or a vacuum leak

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

just checked oil level and found it excessively high. does that mean the fuel pump diaphragm?

 

[99yam40]

Re: 2003 yamaha F90TLRB carb rebuild

Could be, just have to check and see.
Something is dumping too much fuel or you have motor running too cold or over propped and lugging motor

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

any easy way to check the diaphragm other than taking it apart for a visual?

 

[merk175]

Re: 2003 yamaha F90TLRB carb rebuild

update: I pulled the fuel pump off and took it apart and don't see any obvious signs of the diaphragm torn or split. when I put my finger over the suction side of the pump and depress the plunger, the suction side doesn't hold suction....it bleeds air in so I assume the diaphragm is leaking? One other thing that might be significant... I noticed for the last week or two leading up to the problem, the bulb in the fuel line was soft after the boat sat for a couple days. Engine wouldn't start until I pumped the bulb back up. so the symptoms are:

engine won't idle - stalls at idle
getting fuel into the crankcase
engine seems to run ok at high rpm

one last question: how do you get the fuel pump diaphragm out? Do you have to depress the plunger to get the pin out? thanks again to all for your help.

 

[Knoxess]

Re: 2003 yamaha F90TLRB carb rebuild

I have the exact same motor and similar issues. Interested in hearing an update or any other ideas about this issue.