Texas Two Step Taco

[Texasstar]

Will do


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John in your experience with Bultaco Conrods did you chill the bearing and wrist pin first. The wrist pin slides in the piston no problem but when inserted into the bearing and conrod it is a tight fit and does not want to go when inserted unless you chill it or heat the end of the conrod.


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[teazer]

Make sure that the bottom of the piston skirt isn't touching anything, but most likely to be rings hitting/catching on a port edge. Make sure ALL ports are chamfered.

 

[Texasstar]

Make sure that the bottom of the piston skirt isn't touching anything, but most likely to be rings hitting/catching on a port edge. Make sure ALL ports are chamfered.

Thanks Teazer


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[Texasstar]

Not enough cranking amps was a blessing in disguise

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[John Murray]

John in your experience with Bultaco Conrods did you chill the bearing and wrist pin first. The wrist pin slides in the piston no problem but when inserted into the bearing and conrod it is a tight fit and does not want to go when inserted unless you chill it or heat the end of the conrod.


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I've never found them to be that tight; I've always been able to push it through with my thumb with everything at room temp. Is it a new rod?

 

[Texasstar]

I've never found them to be that tight; I've always been able to push it through with my thumb with everything at room temp. Is it a new rod?

No it is not...but both engines required heat to remove the pins...obtw you were right.

Marine deep cycle cell battery. We will see if this will start it. 860 cranking 100 amp hour


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[John Murray]

Not enough cranking amps was a blessing in disguise

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You probably need heavier cables to the starter - everything has to be right or it just won't quite spin. The other thing you might want to look at is the square drive; I used a hex nut on the end of the shaft into a 12 point socket on the flywheel. It's very easy to engage even when you're doing it blind through the fairing.

If it's a used rod I'd be checking that the small end isn't out-of-round. A tight small end would explain the pronounced rocking and noise at BDC. It'll be difficult to get a good measurement of it with normal tools but you could test it with a machined test plug, perhaps with some bearing blue.

 

[Texasstar]

We have 2.41 mm side to side diametric clearance and the limit is 2.5 mm and I don’t feel any up and down.

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[John Murray]

You won't feel any up and down if the small end is tight, you need to take the piston off again and accurately measure the rod eye bore to find out why its so tight. Most likely it's oval shape.

 

[Texasstar]

You won't feel any up and down if the small end is tight, you need to take the piston off again and accurately measure the rod eye bore to find out why its so tight. Most likely it's oval shape.

Will do


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[Texasstar]

You won't feel any up and down if the small end is tight, you need to take the piston off again and accurately measure the rod eye bore to find out why its so tight. Most likely it's oval shape.

You were right!!! Saved me from another top end rebuild! Thank sooo much you! I am going to pull the engine and this crank. The other engine and crank has 1.5 mm small end conrod play and it has a round end.

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[Texasstar]

“You need a cylinder that we can remove the fins from”


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[Texasstar]

bultaco we are going to remove the sleeve bore then bore it to size and nikasil plate it!

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[John Murray]

Don't be in a rush to Nikasil plate it. If you really want to do it leave it til your'e absolutely sure there'll be no more development work done on the engine. Sometimes the port edges will flake or chip if you grind the ports after plating, and sometimes even a light seizure can damage it enough to require replating. And every time it's replated the stripping solution attacks the aluminum, making it chalky so things like internal threads become weak. Two replates is about the limit IMO.

I got so fed up with the damn Nikasil on my Rotax cylinder that I bored it out and fitted a ductile iron sleeve from LA Sleeve. It didn't lose a single horsepower and now I can resleeve it in a few hours (including port matching) or so for a fraction of the price of replating. I can hone it to whatever size I want, I don't have to send it away to be plated and I don't have to deal with weakened barrel material.

 

[Texasstar]

Did you notice a difference between the original Bultaco cast liners vs the LA sleeve cast liners?


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[John Murray]

Not really. The LA sleeves are supposedly ductile iron; I dont know what Bul used for their sleeves but I think they were pretty good quality. The sleeve I'm using now only has about an hour of dyno time on it (though much of that would be at +10k) and it still looks fine.

 

[Texasstar]

Do you have an engine assembly stand for your Bultacos?


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[John Murray]

Oh yes, it's a very complex and sophisticated device indeed. I'll find a photo.

 

[John Murray]

Here it is. I'd be lost without this collection of sticks and nails. I can lay the engine flat on its side with the shafts hanging into the opening below, and everything stays nice and stable on the bench. And because all the shafts sit vertically in the drive side case when I'm reassembling I don't have to worry about shafts hanging down or lining up openings. Once the cases are buttoned up I just flip it over - and again the shafts drop into the opening so it's flat and stable - and fit the primary drive, clutch and side cover. I usually fit the top end and ignition once it's back in the bike. It's stupidly simple but makes splitting and reassembling easy.

 

[John Murray]

Here are some more assembly/disassembly aids - all pretty self-explanatory.