MVVS \ Evo 116CC question (probably the same in other engines as well)

[i3dm]

Hello guys,

On my new Evolution 116CC engine, i noticed after about 4-5 hours run time that the front rubber packing seal (#0204) is protruding a bit from the engine case on one side (probably about 0.5mm), and in order to see if the packing can be pushed in place, i built an appropriate puller and pulled off the prop hub (#1101) and checked the rubber packing, and noticed that it can not move anywhere, and it was probably like this from day one, and i didnt notice it.

What i would like to know is this:

1. how would you recommend trying to push the rubber back in ? its in there hard !!
2. when i re-installed the prop hub (#1101) on the crank shaft, and tightened the hell out of the prop shaft (#1105) im still getting a 0.5-1mm back-forth play in the whole crank shaft (this wasnt evident before i took the hub apart ) where do you guys think this is coming from, and what should i do about it ?

just a note, the crank shaft and prop hub are both cone shaped and tightened against one another.

I did ask the guys at Horizon over the phone, they said that a small amount of play isnt unusual, and shouldnt worry (the engine does run fine BTW) - but im still asking, since this wasnt evident before i took the hub off the crank shaft for the first time.

I added the exploded diagram of the motor to aid in understanding the situation.

Any advice is welcome.

thanks.

[forgues research]

I read your title on EVO 116 and thought we don't have an EVO 116 , then I read the post, you meant the Evolution 116,

Roger

[Kiwi]

i3Dm.

The end float your finding is the rolling tolerence in the ball bearing you see in the exploded veiw (202 and 203). 1mm sounds a little too much but what you should do is run the engine up to it gets to normal running temperature and then see how much end float you have. You may find it reduces a great deal as things tighten up with being hot.

The front packing if it is not showing any signs of oil leakage is OK. It may be installed a tad skew wiff but if it aint broke, dont fix it.

If it leaks you will see an oily mess round the front of your engine and it may even make the engine run poorly.

Kiwi

[KrisW]

Bearing play is a BAD thing when the engine is cold, and gets worse as the engine warms up usually. Depending on how hard you are pulling on the crankshaft to get that play, this may be normal. If it is Front-Rear thrust play, then you have a serious problem (damn that sounded kinky. . . . )

I'd put a dial indicator on the crankshaft and check both your side-side and fore-aft play. You want LESS than .010" of fore-aft play (about .25mm or less), and as little side-side play as possible. . . figure .5mm/.020" here for a good specification. If it is within those specs, I'd say run the engine till it full warms up, then recheck the measurements when it is hot. If they increase appreciably, I'd send the engine in to have it looked at.

Concerning the front seal. . it should be square to the front of the crankcase, and slightly past the crankcase lip as it is pressed into the casing. If it is not, the front bearing may have walked forward in the crankcase (it appears to be only a press fit, no snap ring retainer in the casing), pushing the seal forward at the same time, or causing it to dislodge and be slightly askew. If it is NOT flush, or past the lip of the crankcase, I'd advise sending it back in for a check to find out why. Bearing walk could be causing a misalgnment and improper wear of the front bearing, with the result that you get excessive play in the shaft after only a short amount of run time, as well as possibly being the culprit for the front seal being misaligned.

[dick hanson]

Bearings can be a bit of a puzzle .
On engines such as this one --there are three-- a rear (smaller OD)--the large one right at the front of the counterbalance , and a small front bearing.
Typically -- here is what is supposed to happen:
The small (needle I think) support the rear of the crank and this one is used to allow best breating from the rear induction setup.
The big one --is designed to take the majority of th radial load _not the thrust load -
The front one is the bearing which takes the thrust load and must be solidly positioned .
Some believe the large bearing takes the thrust load -- If it does --then it is doing two jobs thrust and radial load.
So -- typically - if all is perfect -- there is a very slight clearance between the front bearing and the rear bearing . This is done to prevent the bearings from actually fighting each other. Said another way --when the front bearing is loaded under power --the big bearing is centered in it's race .
You may not easily feel this clearance -but it is there .Or should be .
If not - the bearings will gradually wear out or one will move.
When we wer building performance two stroke OS and ST engines -- we sometimes slightly increased the shaft to bearing clearance - making a sliding fit -not a push fit.
Then, we would add a tiny shim behind the front bearing such that the crankshaft was moved rearward a little -- this prevented the large bearing from eve being loaded other than in the center of the race.
On our gassers - depending on which type you run -- the clearances are different -as some have a large bearing on either side of the crank throws - and if you have an issue with the bearings - go to the manufacturer - what is correct for your engine can be all wrong on another one .

[KrisW]

Actually, the bearings function in this fashion:

Rear bearing, either needle or ball, depending on the manufacturers choice. On the 116, there is no rear induction valve, and the reed is above the crankcase, so it is actually a bottom induction re-routed so that the carb faces to the rear. Rear bearing supports the crankshaft only.

middle bearing .. handles both radial and thrust loadings because of the way it is pressed into the crankcase and the fact that the crankshaft tries to pull forward through the bearing .. thus it acts as a thrust bearing in this case as well.

Front Bearing. . handles mostly radial loading (keeps the front of the crankshaft true) and also has a minor pre-load built in concerning thrust. Depending on the crank hub design, it can also be a thrust bearing in a pusher configuration.

When the bearings are installed, they are usually both installed at the same time, then the crankshaft pressed into place through the rear of the front case half, with a collar holding the front bearing from moving during the pressing. This provides the best and tightest "pressed in place" positioning of the bearings. The prop drive hub is then installed, and usually rests up against the inner race of the front bearing (At least it does on BME's. . 3W and DA it does not) and effectively "locks" the crankshaft in place.

In any engine, though,any movement of the crankshaft, expecially fore-aft, is a sign of problems most of the time. There can, and usually is, a slight amount of radial play when the engine is warmed up, but the rest of the time it shojld have a decently snug feel to it.

[dick hanson]

What I was addressing is the fact that duplexing a set of bearings is not good practice.
Duplexing is where two bearings on the same shaft are preloaded against one another . One of the two should always be free to take up axial length variations .
If you check with Horizon , they can clarify this setup on the 116. If possible check with the specialist on these , Mr Booker.