Sharpeye22

Need help,
I changed the bearings on my Saito 72. Now when I tighten down the prop the engine gets so tight the prop will not turn. I can loosen the prop nut and it will then turn. Any suggestions what I may have done wrong?

SrTelemaster150

Bearing not seated all the way. Debris under the outer bearing race might be keeping it from seating all the way.

Sharpeye22

I guess that means putting it back I. The hot oil bath and pulling the bearings, checking them and the seat real closely and reinstalling them.

Thanks for the info.

Ernie Misner

Try warming up the case and with the backplate removed give the crank a few taps forward before you tear it all down.

Ernie Misner

Are you guys ever using the stock carb when converting them to gas?

Thanks,

Ernie Misner

SrTelemaster150

Just a guess on my part, but if the bearings aren't seated all the way you will be putting compression on them binding them when you tighten the prop nut down.

Try putting some tube spacers under the prop nut leaving off the collet & drive hub. If you can tighten the prop nut down then W/O binding up the bearings the problem might be your prop hub interfering W/the front of the case. If the bearings bind up, then your problem lies in the bearings.

SrTelemaster150

It doesn't work very well. The fuel delivery volume is a lot different for gasoline compared to alcohol. Some sort of on demand regulator can be employed though.

jeffie8696

When tuning the intake for a drag race engine it is common knowledge that longer runners increase the low end torque, a large plenum increases the top end power.

Sharpeye22

All good suggestions, I will try each. Thanks

a70eliminator

Like the comments about the cars. My moments of madness included a Ford Zephyr with a fuel injected 289 Ford up front, with jag drive line and an FX Holden wioth A9X front end and a wrong way 396 Chev up front through a 2 speed C$ (I think).
My current ride is a fully homogulated Datsun 260Z that I guard (read hide) here in FNQ from my sons and daughter.
Re the 150 is that the twin plug version. I had one of those and a twin plug 120 that I swapped for a G500 ST plus numerous go faster bits and an OS40P BIG mistake.
[/quote]

Here's my 26 MPG, 4200# "Redneck Mercedes" doing some passes.

1st, some N/A passes:




Here's a pass W/a 125 shot of nitrous that ran out just before then traps. It was a 5.7 powered LX record at the time.






Wow! low 11's with the family sedan 129'sh MPH to the grocery store I tell ya! Dang that mopar honks on. good job on that!

Hobbsy

My Feedback: (102)

Save yourself all that trouble, if you have a 6" vice place a socket the same diameter as the outer race on the rear bearing and wood block across the nose and squeeze that rear bearing into place. If the front were the culprit the prop nut would have seated it. Don't use the end of the socket with the square hole in it, it would push on the inner race, you don't want that.

Cougar429

My Feedback: (3)

I find if the bearings were not seated correctly and you tightened the prop nut down enough to seriously bind the crank then likely you pooched the bearings. To add that much drag you would have deformed either or both the rollers or bearing races.

It may not seem like it if the bearings are then seated with the correct spacing and everything tightened down, but I can almost guarantee they will fail prematurely.

You do place some loads on the rear bearing if you use the crank to install it, but if you avoid banging it in place then it should survive. A couple of pointers I've found over the years are the inner bearing races should NOT have to be forced onto the crank. There should be a tight fit, but with both at room temp you should be able to install and remove the bearings with your hands only.

Also, I sometimes fit the rear bearing to the crank before inserting the assembly into the case. Even with the front bearing removed you can get a good indication of alignment. Otherwise trying to see if the bearing is going into the case straight can be difficult. If heating the case you can even grab the end of the crank and pull then into place or lightly push the back end of the crank/bearing pair down to seat.

Sharpeye22

Maybe my method of installing the bearings is wrong. I place the case in a pot filled with enough oil to cover the case with oil and heat the pot to around 250 degrees F. Then I place the inner bearing on the crank, remove the case from the oil bath and slide the bearing and crank into the case. I then slide the front bearing onto the crank, place some washers that are the diameter of the outer race as spacers and with the prop nut I tighten it all down.

Comments?

Cougar429

My Feedback: (3)

That process sounds fine. I use a heat gun myself. Your method sound better as the heating would be more uniform. I clean my motors in a crock pot with glycol and they come out extremely hot. Usually let them cool and flush before reassembly to prevent contamination of the new parts. Clean oil would work just as easily.

If that method was used and there was still binding double check to see if the motor called for a -ZZ bearing as they are usually thicker. Other than that perhaps improper assembly sequence of the crank, spacer and crank gear?

Sharpeye22

I pulled the drive flange and sure enough the front bearing is ever so slightly deeper than the end of the case. So when I tighten the prop the drive flange contacts the case. So it is not a case of the bearings not being seated. The front bearing must be to thin. The saito 72 is the old case. Are the bearings for the old case different then the ones for the new case? I got the bearings from Boca as a kit with front and rear together. I did not specify old case because I did not think they were different since Horizon hobbies only offer one number for the 72's bearings.

Hobbsy

My Feedback: (102)

Here ias the skinny from BOCA the front should be 7mm wide


http://www.bocabearings.com/productd...tSubGroupID=22

Woops, sorry that link doesn't take you far enough, click on "kit components"

Sharpeye22

Here are the ones I got. It says the front is 7mm. In fact all the dimensions are the same as the ones you linked to. I am not sure how to proceed now. I am thinking of machining a spacer. Does the ZZ mean metal shield for my bearings have no shield or seal.

http://www.bocabearings.com/bearing-...-all-models-72

nextofkin

My Feedback: (8)

Sharpeye22
You might have thought of this, if you have the old bearings measure the old one and compair it to the new one.
Hope this helps
nextofkin

SrTelemaster150

The front bearing should have a composite seal.

As long as you have the proper bearings already installed, just make a shim of the appropriate thickness shim stock or, carefully dress the front of the case off W/a mill file. As long as the collar clears the case the few thousands difference in the prop hub location will not matter as long as there is no run-out..

It's possible that the tapered (aluminum) prop hub bore for the collet has been distorted slightly by overtightening the prop nut. That could make enough difference in the final seated depth of the prop hub. to cause interferance W/the case

SrTelemaster150

Actually, I bought the car to tow my camper.

Cougar429

My Feedback: (3)

If your bearing has no seals that would explain it. From my own fun and games from Boca regarding some of my Fox motors I found sealed bearings are usually thicker.

From my own experience sheilded bearings are usually denoted with a Z code for metal and R or RS for rubber or other synthetic compounds, (flexible seals). Double metal shields are -ZZ and double seals come with 2RS.

Sharpeye22

Problem solved. I turned a spacer out of alum. stock. Installed it and reinstalled the drive flange, prop,etc. engine turns over nice now with no drag. I was finally able to crank it up and retune it. Nothing sounds or runs like a Saito.

Thanks all for your input.

Cougar429

My Feedback: (3)

Glad to hear it's up and running. How thick was the spacer?

Sharpeye22

The spacer is .5mm. It could have been thinner and still work I believe but I figured I would error on the safe side.

Ernie Misner

You guys are amazing.