Thread: 1996 Blazer VL100 Restoration to Crappie Chaser

Great detail John, thanks. I'll need it when I tear into my 90 yami maha.

And wow Jamesdean, you write down posts like there's gonna be a quiz on the topic. What commitment. But you're right, write it down, and you'll remember it. That's what I used to do when I was in school.

Now that the Tiller and Bracket are married back together the Upper Casing has to be installed.



The first picture is the new lower Engine Mounts including new bolts. The cast housings that secure the mounts to the Upper Casing were both cracked so these new ones was the hold up as they were out of stock for a month. Once in place I stabbed the Upper Case back in place and secured with the mount bolt nuts.



Slab always use Yamaha Engine Crankshaft Seals, Yamaha Head Gaskets, and a Yamaha Base Gasket. Here I have cleaned both mating surfaces with a blue 2in surfacing pad (scotch-brite disc) very carefully. If done with care old gasket residue comes right off without out removing and metal.



Another lesson learned is to always drop the Lower Unit before dropping the Powerhead back onto the Upper Casing. I have a new theory as to why I had a Seal failure but my Bud who builds these daily told me the seals can get damaged when if trying to align the driveshaft with the Crankshaft on a Powerhead install. I also wash all mating surfaces with Acetone to remove anything that may prevent a gasket from sealing.



Everything is back together except the Head. My Bud made another one for me since the other Head from him only made 130psi.

Well after finding the Crankshaft seals were toast the Powerhead was pulled by me and I dropped it off to a Race Engine Builder friend for some more work. After breaking the Glaze new rings was installed on the .020 overbore pistons, the Intake and Exhaust Ports were worked, another 150Psi Head was installed along with Boysen Graphite Racing Reeds.



I did the 1 hour idle, the gas is double oil. you can really hear the Reeds singing under the Cowl.



I pulled the truck up a bit after a hour and throttled up for a minute to see how it sounded, all good.

The remaining 9 hours of breakin will happen hopefully over the next couple of weeks.

I've had 3 cylinder 2 stroke Yamaha outboards since 1990. They have a particular idle when everything is right and a very detectable miss when it is not. Old Crossflow OMC engines had this issue too when you do everything right to tune it but the lean idle miss or sneeze kinda hangs around. Another principle I live by is "A lazy man does the most work" and this one bit me by not following through. So I'm breaking in the built Powerhead and can hear it still isn't right, the extra shake to the Cowling, the 3 cylinder hit followed by only 2 cylinder hit at idle, kinda weak off idle to butterfly opening when the throttle is ramped up. This can not be tuned out with Carburetor adjusting because the cause is not there. It is not electrical either. I trusted my bud to do 100% work on the Powerhead but he is young, very good at building powerful powerheads for Drag Racing but the 100% follow through isn't there. I should have check behind him but there are lots going on here besides this project so I put it together without my usual 100% nature in practice.



Behold why I had to pull the Powerhead back off. The silver fitting you see right over the 2x4 centered in the bottom of the Powerhead is a Check Valve. This Check Valve drains excess oil off #3 cylinder and during the cylinder's Pulse pushes the oil thru the Check Valve towards the Upper Crankshaft Bearing which my Bud had to replace with no less than 15 hours on the new one. I didn't check this Check Valve when I initially rebuilt this engine, I didn't check it while the powerhead was off, I didn't check it before reinstalling the powerhead, see where I'm going here. So the Check Valve is stuck open, the top crank bearing is not getting oiled properly as the oil is just moving back and forth in the hose. Well fuel/oil mixture is also pooling in the bottom cylinder causing excess enrichment of the mixture creating the miss.



The 2 Check Valves in cylinders 1 & 2 are fine. These Check Valves oil other Crankshaft Bearings.



I'm not sure where this Check Valve is draining excess oil but it also feeds the top Crank Bearing. The top bearing has 2 oil lines on a Yamaha 3 Cyl 2 Stroke. This Check Valve is a different part number than the other three also. Well this one is stuck open too. OMC engines have these Check Valves too and when they are stuck open you can't tune them to idle right until you replace the check valves.

To check for proper Check Valve function you load a syringe with alcohol and attach the syringe to the hose going to the Check Valve. You should NOT be able to push alcohol thru the valve but you Should be able to suck air back thru it. I Should have done that before installing the Powerhead but didn't. My Bud said it was a waste of time. Well all 2 stroke outboards that oil the Crankshaft Bearings this way using check valves can't be tuned to idle smooth as fuel/oil mixture pools in the intake passageways.

Back to why I had to pull the Powerhead.



This fitting is Pressed In not threaded. I had no way to replace the fitting while the Powerhead was installed. A lazy man does the most work. Since this is a 1999 Block I ordered all new replacements. Once back together and running I will follow up here.



Perfection has a price.

Good to know. I'm about to take a look see at my yami 90, it ran rough last time out, which was two years ago! Living on a lake makes me lazy, don't want to go nowhere to fish when I can fish right here. And also, since covid I've traveled a lot less. Anyway, Ima gonna have to check on them there check valves. Them bearing needs the oil to work no doubt, and I wanna see my motor run for a good long time yet. tanks John

Got it done today. Ran the engine, no misses at idle. Ran it on the hose.



When I pulled the Cowl off something was missing. It looks funny.



The Check Valve assembly that is pressed in is not that tight. I was able to carefully pry it out with a small Snap-On Pry Bar. The socket had oil/gas dripping out when I stood the Powerhead up. Check out the fitting, the guts of the check valve is completely missing. Now this fitting and the 2 forward close to the Intake have a shorter skirt than the one check valve back in the middle of cylinder 2.



I ordered all new Yamaha OEM oil recirculation hoses while doing the job.



The old hoses are swollen, loose fitting too.



This is the two part numbers of the check valves I installed.



Coming together now.



After running. It has that slobber I need to run it in the water to burn out the residual oil/gas in Cylinder 3.



I wanted to show how I drop Lower Units as I have gotten older.



I pull all the bolts but one on each side then trim the Lower Unit up placing a chair and a big block and a little block. I leave just enough room to slip the little block on top of the larger block. Once I slip the little block in place I remove the remaining 2 bolts, lift the Lower Unit enough to get the little block out, then I hold the weight of the Lower Unit while sliding the chair out of the way with my foot. This way I'm not holding the all the weight of the Lower Unit while removing the bolts. Works like a charm.

Priceless information, particularly if you own one of these engines like I do. Thanks Roj