3daviator

My Feedback: (23)

I just bought a used 1/3 H9 Cap with this engine. It shakes terribly. I checked prop and spinner bal. and they are good. I indicated crank. it was TIR .007 at the pickup ring and .020 out on the prop hub. I tried calling Bme this morning a couple of times but no answer. anyone had one of these cranks straightened or replaced? If so what was the cost. Anyone updated one of these motors? Thanks, Rick.

Desertrat

My Feedback: (2)

Mine shook really bad at idle, and more than I thought it should at peak during the first half gallon. Not knowing exactly what yours is doing, I cant say yours isnt bent, but here is what I did, and now the vibration is acceptable: lean the low end needle to the max possible - I leaned mine until it wouldnt transition, then richened back to the next setting that would. That alone removed almost all of the shaking tendancies, especially the rough idle. The more gas I run through it, the smoother it gets. Keith says the 102 is smoother still, and will give you approximately 300 rpm increase at peak, but it will cost you another $350 for the upgrade - I opted to get on the list for the 110 as I didnt think the upgrade cost was worthwhile when the 110 is going to be a monster, will have same dimensions and weigh less.

3daviator

My Feedback: (23)

Thanks for the reply. This engine is used and is already broke in as it was used before it went into the cap. I haven't tried leaning it out on the low speed yet but I can't believe that the amount of crank runout I measured is factory or acceptable. I think .002 tir would be bad enough let alone .020. With everyone using CNC equipment they should be to hold this to .001 tir or better easily. I need to fix it or get my money back so holding out for the new motor isn't an option. What is included in the upgrade? Is that price just the parts or is that the price sent to BME. I wish BME would answer the phone.

Thanks again. Rick

Antique

My Feedback: (4)

It's definitely bent..Anything over .002 at the end of the hub extension is unacceptable...Try indicating the surface of the hub to see if it's 90 degrees to the crank..It's probably causing tracking problems at the tips of the prop.....

captinjohn

RCIGN: If a person set-up a dial indicator at the very tip or near tip of prop.... then turn prop 180 degrees to see the position of other tip...would that be another way to varify this problem? Could try it with a couple of different props and if the tips did not have about the same reading...something is bent or ???? Thanks Captinjohn

3daviator

My Feedback: (23)

Thanks for the reply. Yeah I checked the face of the hub also. because of the serrated face I bolted my degree wheel to it (7" dia) and at the outside it's out at least .050 or more ( I didn't bother to actually indicate it) but thats at 7" I can only imagine what it's at @ the tip of a 26" prop.

Still no answer at BME.

3daviator

My Feedback: (23)

Thanks for the reply. Yes that would definately be another way to see if it's bent without the need for an indicator. Although with the motor still mounted in the plane it's hard to turn it over with-out something moving which is why I mounted the indicator directly to the engine. I wanted to see how far out it was so when (if) I get through to BME he may be able to tell me based on past experience if he can straighten it or not.

Thanks, Rick

3daviator

My Feedback: (23)

I'm sure its possible. I have a press and a lathe. The only problem I have with doing this is that I paid for a "good" engine and don't feel I should go to the trouble and expense of fixing it myself. I wouldn't even attempt it without the crank out of the engine though. We'll see. Since I found the problem the guy I bought it from hasn't returned my e-mail and BME isn't answering the phone.

Thanks, Rick

Desertrat

My Feedback: (2)

As I remember. the 102 upgrade was crank and crankcase, price is for complete upgrade, he does the work, sounds like it could be just the thing for you. Before christmas Keith said the turn around would be in the 3-4 week timeframe, may be better now.... may be worse. I cant believe you are having a hard time getting through to him, he must be out or something, I've called him 6 or 7 times in the past, and gotten him every try <shrug> good luck.

Big_Bird

My Feedback: (1)

Before you go bending it back into shape, it may not be bent at all. It may be twisted from a prop strike. Any accident that will bend a crank will usually twist a crank on a twin. Runout will be the symptom.

Just a thought,
Ken

JLB

My Feedback: (2)

I built and sold Sachs conversions for a few years and "straightened" several cranks from engines that had suffered those sudden stops caused by contact with terra firma. Cranks don't actually bend but do in fact twist the counterweights on the crankpin caused by the front half of the crank stopping while the back half continues on for a very short distance. This means the front shaft and back shaft are now rotating on two different centers. A press is definitely not the way to fix a crank. A lathe, vice, big hammer and lots of patience is required and it's best to send it back to the engine builder. I've seen many cranks made "perfect" with a press go right back out when reinstalled in the crankcase.

3daviator

My Feedback: (23)

Thanks for the responses. that makes perfect sense about the "twisting" or turning on the pins. I'm used to working on 4-stroke motorcycle engines that have solid cranks and use split con-rods.

JLB, when you "straightened" the cranks did you chuck on the back end of the crank and then tap the counterweights(with chuck locked) to get frontshaft and backshaft to the same ctr? I've never had a twin apart so I'm not quite sure what the crank arrangement is. Sounds like worst case senario I will ruin the crank and have to buy a new one anyway.

My hope is that the guy I bought it from will pay to have it fixed or maybe split the cost of the upgrade? Any idea how much a crank for this engine might be?

Antique

My Feedback: (4)

Almost any crank WILL bend if hit hard enough, especially those with only one front bearing and a prop hub 2 or 3 inches away from the bearing(G38, Sachs 3.2, US and Quadra 35-42,) and some others..The long cranks on some of the other engines that don't have a bolt on hub are usually soft and bend easily......If you bore a 1 inch steel block to exactly fit the crank you can indicate the end of the taper and see the runout..A lathe chuck good enough to do this wouldn't be for very long.. Hubs can also bend, the 6 bolt Sachs conversions by A&M and copies thereof are a good example...Most cranks will twist along with the bend...Hubs also bend..I have a 3W 150 hub here that was hit so hard that the rear of the taper, next to the case, is deformed about 1/8 inch....The thread broke off the end of the crank on that one...
FWIW..The cranks most resistant to bending are the cantilever cranks with the taper only about 3/4 long, from the front of the case..The front bearing is only about 1/8 inch away from the case and such a short shaft is really hard to bend...There's no way one of those can twist...
Putting an indicator on the end of a prop to check runout is mostly useless--Nobody's prop is that good.......
Best way to get the hub perfect is to bolt the engine upright on a mill table and use a nice sharp carbide cutter to face the hub while turning it slowly by hand...This gets it exactly 90 degrees to the crank......

3daviator

My Feedback: (23)

I finally got thru to Keith at BME and he said based on the numbers I told him the crank is definitely bent. (twisted and bent probably according to him) He said it should be no more than .002 tir out by the prop. BTW, this is the 2 bearing engine with a long prop hub.

Cost to fix: Send complete engine to BME, $250 to "straighten" .

Do it yourself $175 for new crank + gaskets etc.

Upgrade to 102: includes new cases(3 bearing),
new longerstroke crank, hone clyinders, new rings,
gaskets etc. $450


It looks like the guy I got it from is going to do the right thing and pay the $250 to have it fixed.

When in doubt use a wood prop. less chance of damage!

Thanks again for all the input. Rick

Desertrat

My Feedback: (2)

darn... missed it by 100 bucks... lol, I knew it was too expensive for the minor increase in power.
glad to hear it sounds like its all going to work out for you.