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- Опубликовано: 25 май 2017
- 20170525151444 1
1990's #101 evo sportster 90ci big bore lowerend assembly motor case machining tatro machine
just another bail out job from another shop. they got in over their head and call tatro machine for help.
as you can see this motor had a lot of problems that needed to be corrected or it was going to be coming back to the shop very soon. previous bad machining needed to be corrected. after all the fitments were checked and corrected the 1st shop was going to assemble the motor and bike.
this motor is 90ci with axtell 3-13/16" + .060 big bore cylinders with the stock 3-13/16" stroke crankshaft.
tatro 
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Yea, a larger bolt to start with , then a triangle shaped double arch & a re-die. Drill the top larger & use a washer.
Hey Tatro ... Wouldn't it be better to drill the case rite through and tapper the bolt and at least you'll be able to tighten the bolt and keep the tapper in the position and put enough tension on the bolt . So at least you've got a lot more bolt to work with there than rounding it off ...
Cheers from Down Under. ..
read the other replies.
tatro
I'm pretty sure the guy who said something about straight was actually thinking that was the bolt he was using ...He obviously was not on the same page ...Won't the shoulder of that bolt push off of what's left of that tower that was broken ?
You gotta tell your boy running the camera that the scary welder can’t hurt him if he looks at it through the camera. If he wants to look away more power to him but the camera doesn’t have retinas to burn....
One last thought/question, on an Evo Sportster motor what’s the biggest, reliable engine you can build ci-wise? In short I guess I’m asking if you had a bone stock 883 or 1200 and you wanted a hot rod, how would you build it?
87ci from bore and add stroke as needed.
tatro
im wondering why they didnt trim the jug skirts instead???
Hey Tatro...Cheers. I would have torqued the unmollested bolt in and then scored the profile of the bolt that was interfering on both cylinder bores with a scratch awl and then removed the bolt and then die grinded the scored part away. You would be left with "more meat" on the bolt that way. Just my 2 cents...
and then if you turned the bolt it would dimple the cylinder bores and case piston problems. i have also seen broken cylinders when people turn these bolts or try to take them out without 1st taking the topend off. i do things the way i do because i think it is the best way for the applications. if someone turns this bolt it is not going to do any damage but it might break off which will tell you that you did something wrong and maybe should find someone that knows what they are doing to work on your bike.
tatro
True about the possibility of damaging the cylinders if not removing top end first. Why anybody would want to re-torque the bolt after its' installed or remove it unless splitting the cases (would remove the top end anyways) is beyond me but anything is possible! Still would do that over turning the bolt that thin but I see your point...
All the other rookies are throwing theirs in, here go my pennies (questions actually) to weld into your lathe for thumb tabs, which is an awesome idea by the way...
First, can't believe you pulled that off on an engine lathe! That table must be nice and tight! Well done!
Now... Here's the dumb question to go with the others... Instead of just bending up, what about getting the center cherry and forming between two pieces of that pipe for the rough cylinder shape to allow for cylinder fitment? Provided the press can be controlled so it's not too thin in the center? Just an idea I had....
Regardless, I have a 96 sporty, so this was INVALUABLE information. Thanks.
that is all fine until you turn the bolt just a little bit and now nothing lines up and you bend the cylinder spigots. that is why you make it round so that it does not matter what the rotation of the bolt is.
tatro
Told you it was a dumb question. Yep. That makes perfect sense! Knew you were doing it that way for a reason, but I still had to ask. I'm just that little bit smarter now. Thanks.
I have one of those lathes and they are an older, belt drive, excellent quality Taiwan design (Taiwan made, and makes, some quite decent machine tools but older is often better) made by more than one company. Eyeball the style in case you can score one. Mine even had the six jaw chuck, a three jaw and four jaw. Enco is another good affordable used lathe.
You can't get past the fact that the bolt will still have to be thin, no matter what way you fasten it! If the torque number has to be way down so the bolt is not stretched or snapped, I'd say keep it threaded into the case half!
even a thin ass bolt or screw will help hold the cases together. a little pressure goes a long ways in this spot.
tatro
Peter Tyler yeah, it looks a little funky, but there's a bunch of 88" & 90" XLs out there with this same deal with the bolt between the cylinder spigots, but I think most people would be likely to run into the limits of strength of the OEM pressed crank assembly with hard usage... that bolt prob'ly ain't gonna ever give the owner an issue
love the jandals Fred
couldn't you of "notched" (set up in the mill and created a flat on the cylinder skirt to accommodate that bolt.?) seems I've seen that before...?? there's enough meat on the skirt and that far down there's no pressure to crack or split the skirt that way you don't lose the Integrity of the bolt....
somewhat but these cylinders are very thin. at .060 over there is not much left ti work with. a little here and there is better then cutting all in one spot on these deals.
tatro
Tatro Machine I'm a dumbass... I should have watched the other videos on the cylinder fitment.. I knew it was going to be paper thin but you make it look easy Tatro nice work
That bolt isn't particularly vital. If it were, the slick mod would have been to mill a steel fitting to place a round dowel in each end of the bolt hole and have the clamp bolt outside the case between the cylinder flanges. Not hard to to but no one has bothered so that tells me even drag motors don't need it much. Stroker Sporties have been a thing since the 1950s.
you could install the jugs then pin drill the skirts and then bolt / pin them in with the bolt... May Be???? bad idea????
not a good fix. the pins or bolts will work loose and let everything float around. this lets the cylinder run very hot because it is not attached to the cylinder to dissipate the heat.
tatro
spend 25 dollars and buy a new liner nouthen last forever