Shock Treatment Done

[Wally]

I've had a persistent miss at idle on my Yamaha 90TLR (2 stroke) since I got it with just a few hours on it. I've done the SeaFoam shock treatment and it helped but there is still a little bit of a miss at idle that sometimes stalls the engine.

The diagram for the carbs shows a pilot screw behind a brass plug. I would like to clean them and shoot some Chemtool in there but I don't see how one gets the brass plugs out. They are flat and sit flush in the hole with no groves or obvious pry points. Does anyone know how to remove them to gain access to the pilot screws?

[jb123]

take them completely apart, clean every orifice,replace any defective oring,gasket or aluminum washer.

[Ken]

Wally,
I don't know how to remove those plugs w/o destroying them - I think the factory wanted the pilot screws left alone ?
But I don't think that is where your problem is.
Each carb on your 90 has two jets - a low and a high speed. And I believe you have to tear the carbs down to get to them. Sounds like the low speed jets are clogged.
Even though your motor has few hours on it, if the motor was allowed to set up for more than a month w/o being run, and the storage procedure in the owner's manual was not followed, then there is a good chance the carbs are clogged.
A teardown and cleaning may be in order.
Good luck [img]smile.gif[/img] ,
Ken K

[Wally]

Thanks for the info. I have one more question.

My motor has a red plastic emergency start valve near the carbs. There are three positions shown on the air intake cover for this valve (Normal, Open, and Closed). The valve rotates about 180 degrees to the right from Normal to Open to Closed. The manual says this valve should be Closed unless opened to help start the engine. I've used it once to help start a cold engine but otherwise it has always been left in the Normal position. I've never put it in the Closed position. Should this valve be left in the Normal or the Closed postion when not needed to help start the engine?

[Mr. Ed]

Normal position, rotated all the way counter clockwise. What year is the motor? I think Ken is correct, in that you need to tear the carbs down to get to the jets. I think these carbs (depending on year) are the same set up as my 70 hp and they are easy to tear down and stick a kit into.


Ed

[Wally]

It's a 2005 90TLR. Besides 3 carb kits and a shop manual, what else is needed to rebuild the carbs?

[Mr. Ed]

Whenever I do carbs on anything I like to soak the carbs in cleaner. You can get a 1 gal bucket with a little basket that works well. Any NAPA should have them. Also blow all the little passages out with air.

All you will find in the kit (at least for the 70 hp) are the top cover and bowl gaskets, needle and seat, float pin, O-ring for manifold seal, and a couple other small O-rings. Being that it is only an '05 ... I'm wondering if you couldn't get away with using the gaskets over. They are a formed molded rubber (of some type) ... not a fiber gasket.

Ed

[Ken]

Wally,
You are going to need only ONE carb kit, not three. One kit should have enough parts for all three carbs.
Check with boats.net, sponsor of this forum, great prices and service, and they will tell you if one kit is enough.
Good luck [img]smile.gif[/img] ,
Ken K

[Wally]

As much as I hate tearing into an engine under warranty, I hate paying the dealer several hundred dollars to clean a few specks of varnish out of nearly new carbs even more.

So, I've taken the plunge. I ordered the shop manual, the carb kit and picked up an expensive bucket of carb cleaner with a basket at the NAPA parts store.

While waiting for the kit and manual I've taken the carbs off the engine and partially disassembled the top carb. The only problem I'm experiencing is with removal of the jets. Neither jet on this carb will budge loose.

For the sake of those considering performing this proceedure themselves, I'll report back after I'm finished to let everyone know if the proceedure solved my engine's idle problem and how much trouble it was to complete.

[Mr. Ed]

Oh, I forgot about the $$$ on the carb cleaner!! Did not have an issue getting my jets out, but one other thing ... If you replace the float needle seats you will probably need a thin walled socket for clearence. The rest should be easy.

Are you sure you only needed one kit?? The kit for my 70hp only did one carb (it was a yamaha kit, not after market), I have seen others that did more than one carb.

[Wally]

It looks like one kit does one carb so I ordered two more. Nope, those jets won't budge. I guess I'll let them soak in some wd-40 for a while and try again later. The big one is starting to chip instead of coming loose and the smaller one broke the screwdriver blade!

[Wally]

I'm not sure if new main jets are included in the carb kits but I'm going to have to (carefully) drill one out that won't come out and replace it. All the others came out OK. I am seeing some gum or varnish on some of the jets, so I'm thinking that is where my idling problem is coming from.

[Mr. Ed]

Wally -

Jets are not included ... at least for my 70 hp.

Ed

[Wally]

While I've got the carbs apart I've looking at some orifices (on the carbs, of course) and noticed something interesting. On the left front top of each carb there are two holes that appear to suck some air into the carb when the engine is running. The first, shorter hole goes directly into the carb body allowing anything squirted (Chemtool maybe)in there to go straight to the fuel bowl. The second longer hole goes to a small cavity that feeds air to the main jet and to a lesser degree to the secondary jet. Anything squirted in that hole with the engine running would be sucked right into the jets.

For future reference, might this not be an easier way to do a quick shock treatment on those Keihin carbs?

[Wally]

There's no joy in Mudville. While putting the bottom carb back on I dropped a small nut and washer into the cowling. I found the washer but suspect the nut may have dropped into this quarter sized cavity where the shift lever rotates down to the gearing. There is a rubber expanding ring right in the middle in front of the block where the lever goes down through the cowling. I can't see in it or feel to see if the nut dropped in there and can't tell how far it might have dropped.

It looks like this hole is made so anything (water, dirt, etc.) that gets in the cowling will drop down in there. Any ideas how to check that hole for obsticals, like a nut, short of turning the motor upside down or tearing it appart?