Yamaha 150-HP Two-cycle: Alternative to $600 Carburetor Repair

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Author Topic:   Yamaha 150-HP Two-cycle: Alternative to $600 Carburetor Repair

grocks posted 07-28-2010 12:25 AM ET (US)
[I] took my 1990 Yamaha 150-HP two-cycle into the shop the other day [because] the motor was running rough at low speed. [The] motor was running fine at high RPM. The service tech told me that the carburetors need to be taken out and cleaned [at a] cost of about $600. [Although] the motor has run very well in the past, I hate to spend this kind of money on a 20-year-old motor. I think we left some gas in the tank over the winter and it now has caused problems. Is there anything I can try to do first on my own to try to fix this problem?
jimh posted 07-28-2010 01:24 AM ET (US)
What usually happens in a situation like this is the owner disassembles the carburetors himself, tries to clean them, and reassembles them improperly, perhaps losing a few parts in the process. The professional mechanic then charges $800 for the repair because he has to add new parts.
You could try to add solvents to the fuel which might dissolve whatever residue in the carburetor is causing the problem. However, gasoline itself is an excellent solvent, so if gasoline cannot dissolve the residue, you will need a very strong solvent. Pouring really strong solvents into your fuel and hoping they will just target the residue while leaving everything else intact is wishful thinking. A really strong solvent in the fuel might dissolve something else besides the residue causing the problem. This is why the usual technique to remedy this problem of residue in the carburetor is to remove the carburetor, separate it into its component parts, and immerse the metal components in a strong solvent. The rubber components are discarded and replaced with new rubber components. The strong solvent cleans the residue from the metal parts. The parts are then sometimes burnished or polished to insure they operate well. Then the carburetor is reassembled and re-calibrated with the throttle linkage.
You do not have to be a theoretical physicist to perform this procedure, but you do need some guidance and will probably learn from experience what pitfalls await the novice.
frstevec posted 07-28-2010 09:46 AM ET (US)
Greetings,
I just cleaned the top carburetor on 115 Yamaha 1988.
Bogging on full throttle, poor idle and little fuel getting to one cylinder prompted me to clean the carburetor as a first step in fixing the problem. After watching a video on themarinedoctor, I took the carburetor apart and found that I could hardly blow through one passage after I removed all the jets. I found corrosion on the carburetor body inside orifice that I scraped off until it had as open flow as the matching one on the other side.
I reassembled it and reinstalled it. Result was smooth idle, no bogging, and full four-cylinder operation! The Bad news was I saw gas leaking into the water. JMH's point taken- I had failed to tighten the slow air jet screw (my screw driver was too big and later I forgot that I had not tightened it.) So, I took the carburetor off again and found the screw laying on the lower carburetor, installed it and reassembled and I'm now able to hit 36 mph whereas before, 30 mph was WOT.
Watch the video and tighten all the screws. Steve
http://www.themarinedoctor.com/yammieweb.wmv
grocks posted 07-28-2010 10:29 AM ET (US)
[I]s there any [chemical, compound, solvent, elixer, additive, or potion] that can first be added to the fuel or sprayed on the carburetors before they are taken apart? [O]r is [trying to clean a clogged carburetor by adding solvents to the fuel or by spraying a solvent on the carburetor] just a [waste] of time.
Buckda posted 07-28-2010 10:50 AM ET (US)
Do you run ANY additive to your fuel right now/before this problem?
I like to keep Sta-Bil in my fuel unless it will be used within a week or so. I also run a "shock" treatment of cleaner - like Sea Foam - in my tank a couple times a season.
I do this with my truck as well, although I generally never need the Sta-Bil since I consume the fuel quickly. I do, however, run a heavy dose of Sea Foam in my truck tank a few times each year during long-trip events when the engine will be good and hot and will burn the treated fuel quickly
That said, it is pretty much inevitable that a carbureted engine will eventually need to have the carbs removed and cleaned periodically. That is one of the advantages of the closed-system EFI and DFI modern motors.
Tohsgib posted 07-28-2010 11:06 AM ET (US)
Get a 6 gal tank and fill with gas and a full bottle of Berryman's B12(liquid, not aerosol) which can be bought at WallyWorld or Autozone, etc. Run it through but make sure you don't run the tank dry, you will want it to sit in the carbs overnight. It might run rougher than normal with the mixture but this stuff is unreal. Don't spill it on anything with paint on it. Next day run the tank dry and switch back to your normal tank that is filled with fresh plain fuel. Read the directions and add B12 to your main tank with what they recommend, not a shock treatment like I mentioned above. If engine is pre-mixed, don't forget to add oil. If you REALLY want to shock the hell out of it, run it on a bottle of Techron and gas 50/50 and let sit overnight before it runs dry. That will not only clean your carbs but will decarbonize the snot out of your engine. DON'T do it in your driveway unless you like black stains on it.
Tohsgib posted 07-28-2010 11:08 AM ET (US)
Lastly, go buy a carb cleaning pot, remove your carbs and soak them for a couple days, might/should work without taking them apart. If you know how to change your own oil, you can figure out cleaning/rebuilding carbs.
Tohsgib posted 07-28-2010 11:10 AM ET (US)
Lastly lastly, I bet if you remove the carbs and take them to ANY mechanic (car, boat, motorcycle) it would be less than $50 a carb to clean. Send them to me with a check for $150.
Blackduck posted 07-28-2010 11:50 AM ET (US)
A bottle of Techron added to a tank of gas will work wonders.
grocks posted 07-29-2010 03:02 AM ET (US)
[Okay.] I like your ideas. [Should} I use Berryman B12 or Techron? I have used Yamaha Ring Free from time to time, but this past winter the boat sat in the garage and was not winterized. The motor is old but [its] carburetors seemed to be fine in the past.
jimh posted 07-29-2010 09:56 AM ET (US)
Spraying or applying a solvent on the carburetors will not do much except to remove the paint or other finish on their exterior surface. Carburetors are made from different materials. Some are aluminum castings or casting of other metals, and some have plastic parts. They usually all have gaskets made of cork, rubber, or other non-metallic material. Exactly how all those materials will react to a solvent sprayed on them is hard to predict.
Introducing a solvent in the fuel may produce an improvement, however, if past experience is any guide, there are many carburetor problems relating to a need for cleaning or removing residue from the passages of the carburetor which cannot be remedied by adding a solvent to the fuel. Particularly in the case where fuel was allowed to remain in the carburetor and evaporate over a long period of time, the residue that remains is typically not going to be removed by fuel with an added solvent. If adding a solvent solved those kinds of carburetor problems, there would never be any cases of carburetors being removed, torn down, cleaned thoroughly, and reassembled.
The initial problem presented in this discussion is one of rough engine run characteristics at low speed. The low speed orifices or jets of a carburetor are the smallest in diameter, and it would be reasonable to assume the easiest to become disturbed or blocked by a residue.
There is not much harm in adding a well-known fuel additive to the fuel in the recommended proportion, but I would not expect that it will be certain to remedy the problem of clogged passages in a carburetor. It may help.
Tohsgib posted 07-29-2010 12:17 PM ET (US)
B12 is stronger and only like $3.29. Techron is fine but costs $8. I would use B12 for the shock. If you use pump gas, fill tank with Chevron, it has Techron in it already.
adlert posted 07-30-2010 11:25 AM ET (US)
When I was in training school I was taught that carb cleaners and the like had no place in the repair of conventional 2-stroke engine fuel systems. As jimh pointed out, the depth of the cleaning will always be unknown and additionally, you risk adversely affecting other materials (gaskets) that you don't want to damage. Many of these solvents are hell on the softer materials used in carbs. If I remember correctly, it was pointed out to me during training that simply mixing a solvent into a fuel system that carries the engine's lubrication oil is obviously a bad thing. The solvent seriously compromises the oil's ability to do its job. Seems intuitively correct to me.
Another thought scares me even more. In your case you seem to have a low speed problem only...but, what if you in fact also have partial blockage in a high speed circuit? This happens frequently. The high speed circuit is partially blocked but open enough to allow that cylinder to run, albeit lean. Bad things always follow. Many times I've received cases where the owner had some sort of a bogging problem or high speed running problem and the short-cut fix of adding a solvent to the fuel supply "fixed" the problem long enough for them to go out for a few trips and blow a cylinder.
In my opinion your engine is asking you for a proper carburetor cleaning. I'd recommend just that. Do a general engine health assessment first to convince yourself it's worth it. Regardless of what you chose to do, make darn sure you've got every WOT RPM you ever had, or should have given your boat, engine and prop choice.
Tohsgib posted 07-30-2010 11:41 AM ET (US)
I agree with you 100%...ok 95% because what I described above my friend was taught at Yamaha school. They even said that you can run an outboard on straight Techron(as long as oil injected or you add oil to Techron) and do your best to keep it running until you used the can. It can actually free up a stuck ring. I had 15lbs lower compression on a cyl and did just that and it brought it up to only 5lbs after a couple tanks of running. As far as running solvents in gas all the time, why should you and yes it can eat gaskets etc over time. Again we are talking about a shock treatment.
grocks posted 07-30-2010 11:53 AM ET (US)
Thank you all for your help. I will work on the shock treatment this weekend and report back. Looks like we will be cleaning them sometime soon. GR
grocks posted 08-27-2010 01:02 AM ET (US)
Over the past three weeks I have used your recommended shock treatment. Have run the motor for at least 20 hours and yes it seems to be running much better at low speed and is better as well at high spped. I will still look to get the carbs cleaned later this fall when our boating season is over thanks again for all your advice.
pglein posted 08-27-2010 07:47 PM ET (US)
The alternative would be to buy a $50 carburetor rebuild kit and take it apart and clean it yourself. It's really incredibly easy if you are even remotely mechanically inclined. When a carburetor has been fouled, there really is no replacement for a good old fashioned, D.A.R. (Disassemble And Reassemble). Shouldn't take you more than an hour or two.
grocks posted 08-28-2010 03:00 AM ET (US)
I wish I new how to perform this task but have no knowledge or experence.

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Author	Topic: Yamaha 150-HP Two-cycle: Alternative to $600 Carburetor Repair
grocks	posted 07-28-2010 12:25 AM ET (US) [I] took my 1990 Yamaha 150-HP two-cycle into the shop the other day [because] the motor was running rough at low speed. [The] motor was running fine at high RPM. The service tech told me that the carburetors need to be taken out and cleaned [at a] cost of about $600. [Although] the motor has run very well in the past, I hate to spend this kind of money on a 20-year-old motor. I think we left some gas in the tank over the winter and it now has caused problems. Is there anything I can try to do first on my own to try to fix this problem?
jimh	posted 07-28-2010 01:24 AM ET (US) What usually happens in a situation like this is the owner disassembles the carburetors himself, tries to clean them, and reassembles them improperly, perhaps losing a few parts in the process. The professional mechanic then charges $800 for the repair because he has to add new parts. You could try to add solvents to the fuel which might dissolve whatever residue in the carburetor is causing the problem. However, gasoline itself is an excellent solvent, so if gasoline cannot dissolve the residue, you will need a very strong solvent. Pouring really strong solvents into your fuel and hoping they will just target the residue while leaving everything else intact is wishful thinking. A really strong solvent in the fuel might dissolve something else besides the residue causing the problem. This is why the usual technique to remedy this problem of residue in the carburetor is to remove the carburetor, separate it into its component parts, and immerse the metal components in a strong solvent. The rubber components are discarded and replaced with new rubber components. The strong solvent cleans the residue from the metal parts. The parts are then sometimes burnished or polished to insure they operate well. Then the carburetor is reassembled and re-calibrated with the throttle linkage. You do not have to be a theoretical physicist to perform this procedure, but you do need some guidance and will probably learn from experience what pitfalls await the novice.
frstevec	posted 07-28-2010 09:46 AM ET (US) Greetings, I just cleaned the top carburetor on 115 Yamaha 1988. Bogging on full throttle, poor idle and little fuel getting to one cylinder prompted me to clean the carburetor as a first step in fixing the problem. After watching a video on themarinedoctor, I took the carburetor apart and found that I could hardly blow through one passage after I removed all the jets. I found corrosion on the carburetor body inside orifice that I scraped off until it had as open flow as the matching one on the other side. I reassembled it and reinstalled it. Result was smooth idle, no bogging, and full four-cylinder operation! The Bad news was I saw gas leaking into the water. JMH's point taken- I had failed to tighten the slow air jet screw (my screw driver was too big and later I forgot that I had not tightened it.) So, I took the carburetor off again and found the screw laying on the lower carburetor, installed it and reassembled and I'm now able to hit 36 mph whereas before, 30 mph was WOT. Watch the video and tighten all the screws. Steve http://www.themarinedoctor.com/yammieweb.wmv
grocks	posted 07-28-2010 10:29 AM ET (US) [I]s there any [chemical, compound, solvent, elixer, additive, or potion] that can first be added to the fuel or sprayed on the carburetors before they are taken apart? [O]r is [trying to clean a clogged carburetor by adding solvents to the fuel or by spraying a solvent on the carburetor] just a [waste] of time.
Buckda	posted 07-28-2010 10:50 AM ET (US) Do you run ANY additive to your fuel right now/before this problem? I like to keep Sta-Bil in my fuel unless it will be used within a week or so. I also run a "shock" treatment of cleaner - like Sea Foam - in my tank a couple times a season. I do this with my truck as well, although I generally never need the Sta-Bil since I consume the fuel quickly. I do, however, run a heavy dose of Sea Foam in my truck tank a few times each year during long-trip events when the engine will be good and hot and will burn the treated fuel quickly That said, it is pretty much inevitable that a carbureted engine will eventually need to have the carbs removed and cleaned periodically. That is one of the advantages of the closed-system EFI and DFI modern motors.
Tohsgib	posted 07-28-2010 11:06 AM ET (US) Get a 6 gal tank and fill with gas and a full bottle of Berryman's B12(liquid, not aerosol) which can be bought at WallyWorld or Autozone, etc. Run it through but make sure you don't run the tank dry, you will want it to sit in the carbs overnight. It might run rougher than normal with the mixture but this stuff is unreal. Don't spill it on anything with paint on it. Next day run the tank dry and switch back to your normal tank that is filled with fresh plain fuel. Read the directions and add B12 to your main tank with what they recommend, not a shock treatment like I mentioned above. If engine is pre-mixed, don't forget to add oil. If you REALLY want to shock the hell out of it, run it on a bottle of Techron and gas 50/50 and let sit overnight before it runs dry. That will not only clean your carbs but will decarbonize the snot out of your engine. DON'T do it in your driveway unless you like black stains on it.
Tohsgib	posted 07-28-2010 11:08 AM ET (US) Lastly, go buy a carb cleaning pot, remove your carbs and soak them for a couple days, might/should work without taking them apart. If you know how to change your own oil, you can figure out cleaning/rebuilding carbs.
Tohsgib	posted 07-28-2010 11:10 AM ET (US) Lastly lastly, I bet if you remove the carbs and take them to ANY mechanic (car, boat, motorcycle) it would be less than $50 a carb to clean. Send them to me with a check for $150.
Blackduck	posted 07-28-2010 11:50 AM ET (US) A bottle of Techron added to a tank of gas will work wonders.
grocks	posted 07-29-2010 03:02 AM ET (US) [Okay.] I like your ideas. [Should} I use Berryman B12 or Techron? I have used Yamaha Ring Free from time to time, but this past winter the boat sat in the garage and was not winterized. The motor is old but [its] carburetors seemed to be fine in the past.
jimh	posted 07-29-2010 09:56 AM ET (US) Spraying or applying a solvent on the carburetors will not do much except to remove the paint or other finish on their exterior surface. Carburetors are made from different materials. Some are aluminum castings or casting of other metals, and some have plastic parts. They usually all have gaskets made of cork, rubber, or other non-metallic material. Exactly how all those materials will react to a solvent sprayed on them is hard to predict. Introducing a solvent in the fuel may produce an improvement, however, if past experience is any guide, there are many carburetor problems relating to a need for cleaning or removing residue from the passages of the carburetor which cannot be remedied by adding a solvent to the fuel. Particularly in the case where fuel was allowed to remain in the carburetor and evaporate over a long period of time, the residue that remains is typically not going to be removed by fuel with an added solvent. If adding a solvent solved those kinds of carburetor problems, there would never be any cases of carburetors being removed, torn down, cleaned thoroughly, and reassembled. The initial problem presented in this discussion is one of rough engine run characteristics at low speed. The low speed orifices or jets of a carburetor are the smallest in diameter, and it would be reasonable to assume the easiest to become disturbed or blocked by a residue. There is not much harm in adding a well-known fuel additive to the fuel in the recommended proportion, but I would not expect that it will be certain to remedy the problem of clogged passages in a carburetor. It may help.
Tohsgib	posted 07-29-2010 12:17 PM ET (US) B12 is stronger and only like $3.29. Techron is fine but costs $8. I would use B12 for the shock. If you use pump gas, fill tank with Chevron, it has Techron in it already.
adlert	posted 07-30-2010 11:25 AM ET (US) When I was in training school I was taught that carb cleaners and the like had no place in the repair of conventional 2-stroke engine fuel systems. As jimh pointed out, the depth of the cleaning will always be unknown and additionally, you risk adversely affecting other materials (gaskets) that you don't want to damage. Many of these solvents are hell on the softer materials used in carbs. If I remember correctly, it was pointed out to me during training that simply mixing a solvent into a fuel system that carries the engine's lubrication oil is obviously a bad thing. The solvent seriously compromises the oil's ability to do its job. Seems intuitively correct to me. Another thought scares me even more. In your case you seem to have a low speed problem only...but, what if you in fact also have partial blockage in a high speed circuit? This happens frequently. The high speed circuit is partially blocked but open enough to allow that cylinder to run, albeit lean. Bad things always follow. Many times I've received cases where the owner had some sort of a bogging problem or high speed running problem and the short-cut fix of adding a solvent to the fuel supply "fixed" the problem long enough for them to go out for a few trips and blow a cylinder. In my opinion your engine is asking you for a proper carburetor cleaning. I'd recommend just that. Do a general engine health assessment first to convince yourself it's worth it. Regardless of what you chose to do, make darn sure you've got every WOT RPM you ever had, or should have given your boat, engine and prop choice.
Tohsgib	posted 07-30-2010 11:41 AM ET (US) I agree with you 100%...ok 95% because what I described above my friend was taught at Yamaha school. They even said that you can run an outboard on straight Techron(as long as oil injected or you add oil to Techron) and do your best to keep it running until you used the can. It can actually free up a stuck ring. I had 15lbs lower compression on a cyl and did just that and it brought it up to only 5lbs after a couple tanks of running. As far as running solvents in gas all the time, why should you and yes it can eat gaskets etc over time. Again we are talking about a shock treatment.
grocks	posted 07-30-2010 11:53 AM ET (US) Thank you all for your help. I will work on the shock treatment this weekend and report back. Looks like we will be cleaning them sometime soon. GR
grocks	posted 08-27-2010 01:02 AM ET (US) Over the past three weeks I have used your recommended shock treatment. Have run the motor for at least 20 hours and yes it seems to be running much better at low speed and is better as well at high spped. I will still look to get the carbs cleaned later this fall when our boating season is over thanks again for all your advice.
pglein	posted 08-27-2010 07:47 PM ET (US) The alternative would be to buy a $50 carburetor rebuild kit and take it apart and clean it yourself. It's really incredibly easy if you are even remotely mechanically inclined. When a carburetor has been fouled, there really is no replacement for a good old fashioned, D.A.R. (Disassemble And Reassemble). Shouldn't take you more than an hour or two.
grocks	posted 08-28-2010 03:00 AM ET (US) I wish I new how to perform this task but have no knowledge or experence.