A90/A45 Engines

[EatMyShortsRacing]

Folks,

I think the 2 main bearings are the issue. I have tried running my A100 with the steel cage bearings and they seem to have lasted so far. Maybe the way to do it is to run the engine in with the steel cage bearings then change them once you are ready to race the engine.

(note this theory wont work for me because I seem to end up breaking my engines in DURING a race... )

EMS Racing Why waste valuable time breaking an engine in on a club day?

 

[Ian Inverarity]

I would tend to agree that only the two main bearings are the big issue. My original motors that came with polyamide caged mains had metal (maybe brass?) cages for the front bearings.

Nitrocrazed racing: I break my engines in at home to use up old fuel, kill excess lawn and irritate my neighbours!

 

[Andy Slaviero]

Is there any thing wrong with the WIB phenolic bearings? I just purchased a set to replace the steel bearings in my new A-90HP. The only problem that I have now is it seems that when I tighten down my flex adapter it seems that the bearings bind up. I've checked several times and the bearings a seated correcly. The only thing I don't see in this post is about the flywheel design. Mine has a steped ridge that i'm thinking could be causing the flyweel to put to much pressure on the bearings instead of letting it seat on the crankshaft. Is this possible or did I screw something up when I put the new bearings in? ???

Thanks.

Andy

 

[Ian Inverarity]

Andy,

I use the WIB polyamide bearings in my motors, I am sure there is no size difference to the phenolic caged bearings.

If the large bearing in the main case is not correctly seated then I would say that the rest of the engine would not assemble correctly, thus the only thing I can think of that may be a problem is the front bearing not being seated into the case properly. Are you heating the case to install and remove the bearings? The front bearing is made a tighter fit than the rear bearing in these motors, if you heat the case to push the font bearing in the rear bearing will fall out, so you should do the front bearing first.

Have you had much experience with putting bearings in?

Ian.

 

[Andy Slaviero]

Ian,

I did heat the case, and install the front bearing first. The front bearing seems to sit flush with the case and does not look crooked in any way. tThe rest of the engine went together fine and spins freely untill I tighten the flywheel. I do have some experince with installing bearings, but I'm not a pro at it yet.

Andy

 

[Ian Inverarity]

Bearings are nomally made to very tight tolerances, so it would be unusual for one bearing to fit and another to cause a problem.

Sitting flush would seem to be okay. My guess would still be that the bearing is not seated all the way down, but if it is slightly wider you could try carefully sanding the step on the back of the flywheel to reduce the interference. But like Craig said, this should be a small clearance if you are going to run a flex hex.

Ian.

 

[Andy Slaviero]

Ian,

How would I know if installed something wrong? I really don't want to blow it up ot the first run.

Is there any thing else I shoud check for before sanding the flywheel, and being alum. do I have to rebalance it once I'm done. ???

Thanks

Andy

 

[Ian Inverarity]

Andy,

I am just talking about sanding the ridge on the back of the flywheel, and you should not have to re-balance it. Use 800 grit or finer wet/dry paper with WD40 or something like it on a VERY flat surface like glass, rub the flywheel on the paper.

How did you push the bearings in? I generally heat the case over my gas stove top element until I can bubble water drops on it, then using leather gloves push the front bearing down into the case. Everything should be cleaned first so no rubbish gets trapped between the bearing and the shoulder in the case. I push the bearing in as hard as I can by hand. Then I start heating the case in the area of the rear bearing. I put the rear bearing on the crank, then push the assembly into the case. Normally the rear bearing goes in easily. I then lightly tap the outside of the case around the bearings with a small block of wood, and spin the crank to ensure it is free.

Sometimes the fit of the crank and front bearing is a little tight, you have to be careful that when you push the crank in that you dont dislodge the front bearing again.

Ian.

 

[Ian Inverarity]

By the way, if you are going to run a square drive it does not matter if the gap between the flywheel and the bearing is 0.5mm! I have large gaps on my engines because I use square drive and am not concerned by this gap.

Ian

 

[EatMyShortsRacing]

I disagree!!!!

I think that the tolerance between the flywheel and the frint bearing has to be as close (.001-.002) as possible. Otherwise the front bearing is not doing its job.

Craig

 

[Ian Inverarity]

Craig,

Hehe. For example the flywheel I made for the A100 was at least 0.5mm from the bearing. I use only square drive. Using square drive I do not need to use the fron bearing to control the end float of the crank. I have pulled the engine down and found no evidence of the front bearing skidding on the crank. And I lightly relieved the end of the crank to make it a looser fit in the front bearing.... ;D

Ian.

 

[EatMyShortsRacing]

Ian,

and you wonder why it wont rev???

EMS Racing

 

[Ian Inverarity]

Craig,

It is not that loose that it leaks! Hehe. I'll put my A100 up against yours anyday.....

Nitrocrazed racing: Bench racing a specialty....

 

[EatMyShortsRacing]

Ian,

my pre or post Dremel engine??? hehehehe

Craig

 

[Ian Inverarity]

Craig,

No fair, I told you what I did to mine! Pre-dremel of course.... ;D

Nitrocrazed racing: I need a bigger mono for my bigger motor....

 

[waterbug]

Hey you two !!!! which one of you knocked that can of worms over??? now there' all over the floor and table just crawling around !!! WHAT A MESS!!!hehehe!

 

[Ian Inverarity]

Aw mom! Craig started it!

Nitrocrazed racing: Just because I got taller doesn't mean I grew up....

 

[EatMyShortsRacing]

Too late....

Mr Dremel has already been busy...

EMS Racing

 

[waterbug]

O' NO A DREMEL JUNKY !!! THE WORST KIND !!!

I'm sitting here trying to keep my eyes open 2:00 am and calling someone a junky !!! GO FIGURE !!

 

[Mike Bontoft]

Hi Andy

I do'nt know if you got the problem sorted yet but make sure you only have the front part of the crank assembled when you check for clearance. Tighten the coupling and if it begins to binds check to make sure the bearings are seated properly if it still binds most likely the flywheel may have loosened up at some time and enlarged the taper slightly, you will need to sand the raised back portion of the flywheel with 320-400 sandpaper on a piece of glass to get the clearance back 002". The old bearings probably did not bind because some wear had taken place. Pretty much like everyone else has told you. I would also mike those bearings for width before you sand anything .

Mike www.cwiinc.com/engines