HS40 Rupp

#83
BTW I didn’t measure the crank because the only crank I have that is not installed is a late taper crank and I think they might use a different key.

You could try either center punch or oversized key, but it might only need to be oversized on the top. A .005” oversized key might fit the flywheel but not the slot in the crank.
 
#84
bench test "it started ", :). @SAT I cut .003 shim added it with the key & reassembled. It pulls hard, tougher than I thought it would. How do you know if compression relief is working? Wanted to post a short video but says not a good format .mp4?
 
#85
bench test "it started ", :). @SAT I cut .003 shim added it with the key & reassembled. It pulls hard, tougher than I thought it would. How do you know if compression relief is working? Wanted to post a short video but says not a good format .mp4?
Awesome!
Glad you were able to shim the key and get her running!
The flywheel is not a huge diameter but depending on which side you added the shim, you could have advanced the timing a little bit which might make it harder to pull.

I always pull slowly past the compression stroke, then let her rip. As long as you do that it should be easy to turn over.
 
#87
Motor mounted, starts, letting it warm up and adjusting (trying) the carb then notice oil coming out of the governor shaft. To fix it?
Do I have to open the engine up? Man I hope not. 20190828_170608.jpg
 

cfh

Well-Known Member
#88
And yet another reason to delete the governor. Also once you get a slide carb going (be it Japanese or Chinese or a Dellorto), you'll never go back to those tecumseh carbs. And yet another reason to delete the governor, as a slide carb really doesn't work with it anyway...
 

markus

Well-Known Member
#89
How much oil did you put in it? you used the dipstick while it was sitting on the bike right? If you say filled it to the threads on the oil fill hole well you have like double the amount of oil it should have in it. If your oil level is fine then your breather (the valve cover) is most likely clogged or not operating properly and your creating alot of crankcase pressure.

Those shafts can get a lot of wear and slop in them over the years, I have to rebush and used new shafts from time to time when I rebuild....they actually need a little lubrication on them from the crankcase (not like what your seeing though :D) But even if they are slap wore out they wont flow oil out of them like that unless there is some sort of overfill or crankcase pressure problem.
 
#90
I had the oil to full mark on the dip stick, yes sitting on the bike. I'll check the vlv cover. I had it all apart (vlv cover) during the tear down, thought it all looked good. I drained the oil after it ran for a few minutes, I'll refill and verify the level. thanks for the feed back.
 

delray

Well-Known Member
#91
when you first add oil to your new rebuilt engine it will take 21 oz's. after changing it I only refill it to 20 oz's max, there will always be a good oz+ of oil still in the block after draining it. most oil containers should have oil level indicator on the side so you can get a very close reading on how much you put into your motor.this is nothing to do with your oil leak,but now that most standard cheap 5w-30 SAE oil doesn't come with zinc. I add 5oz's of lucas zinc oil and the rest 5w-30 SAE oil. I haven't had no problems with the engine parts/cams getting damage.
 
#92
I was wondering about oil type, I've read where people mention zinc but couldn't find a zinc formula locally. @delray there is a minibike jamboree (1st annual) at Log cabin bar and grill in Rush Lake, wi. sept 7 staring at 9 a.m. probably old news for you.
 
#93
And yet another reason to delete the governor. Also once you get a slide carb going (be it Japanese or Chinese or a Dellorto), you'll never go back to those tecumseh carbs. And yet another reason to delete the governor, as a slide carb really doesn't work with it anyway...
@cfh I wanted to keep my bike as original as possible. Still need a few parts, but it's running. Maybe my next build I'll investigate the slide carb...
 

Cuda54

Active Member
#94
A free small shim is in the white plastic on all of the things you buy. On the inside are little strips of metal at .001 each thick. All of the little white security plastic strips are this way. Just open one and look inside.
 

ELT

Active Member
#95
There is another (cheap) option. I had this same situation on a rupp HS40 motor. Took it to the machine shop and they said, "you know we can take just a tiny bit off the connecting rod mating surfaces, and it will run tight around that worn journal." So that's what they did.

First they smoothed the crankshaft journal. Mine had obvious wear. That took about 2 minutes of work. Then they did some light machining/metal removal to the connecting rod halves so when tightened, then were tighter around the crankshaft journal. That took another 2 minutes.

Cost was FREE (i think the guy felt sorry for me.) The motor actually is still running fine. I don't know what the life will be, but for as little as i use it, the engine seems to work fine.

I was pretty skeptical about the whole thing. But damn the motor was pretty worn out, i really didn't have much to loose. (It had other wear problems too.)

I know this isn't accepted practice, but it did seem to work. You can always go back in the future and have it done correctly, and install a new Arc connecting rod. Obviously don't do this modification to a brand new Arc connecting rod!
My machine shop told me the same thing. They turn the crank pin just enough to make is round and true. They machine a slight amount off the mateing surface of the rod and cap. Then with the cap torqued on the rod it is bored to fit the trued up crankshaft.
 
#96
when you first add oil to your new rebuilt engine it will take 21 oz's. after changing it I only refill it to 20 oz's max, there will always be a good oz+ of oil still in the block after draining it. most oil containers should have oil level indicator on the side so you can get a very close reading on how much you put into your motor.this is nothing to do with your oil leak,but now that most standard cheap 5w-30 SAE oil doesn't come with zinc. I add 5oz's of lucas zinc oil and the rest 5w-30 SAE oil. I haven't had no problems with the engine parts/cams getting damage.
The Stens and Kinetix we have been using says it has zinc in the formula. Been using it for about a year or so now. It’s working for us, well, no lubrication problems so far.
Good thread here.
Thanks everyone.
 
#97
@delray FYI- I used your recipe :) (lucas 5oz/5w-30 15oz), stole my wife's measuring cup, 20 oz put me over the full mark on the dip stick.
Is the dip stick gospel? I removed 3oz and that put it right on the full mark. @markus I checked the breather/vlv cover, I'll try it again tonight to see if the oil leak shows up again.
 

delray

Well-Known Member
#98
I really can't tell you how accurate those rupp dipsticks are? but if your using a legit measuring device. you should be spot on. I don't think 3 oz's under 20 oz's will kill the motor. billet rod can reach a long ways and should splash the oil around good. what little research I have found from gokart engine builders they like to use the thinner oils with zinc, instead of standard straight 30w. thinner oils can lube better in tight clearances and also like to go one step more and run a synthetic. that might be just little over kill for a minibike engine that going to only turn less then 4000 rpm's and maybe wasted money too.
if you ever get into building a hs-motor you will need to build a catch can. anything over 6000 rpm's will find a way to puke oil out of the breather unit or maybe the governor rod hole if not plug.
 

markus

Well-Known Member
#99
@delray FYI- I used your recipe :) (lucas 5oz/5w-30 15oz), stole my wife's measuring cup, 20 oz put me over the full mark on the dip stick.
Is the dip stick gospel? I removed 3oz and that put it right on the full mark. @markus I checked the breather/vlv cover, I'll try it again tonight to see if the oil leak shows up again.

Good luck, Did you see anything out of whack and does the one way/reed valve in the breather work alright/correctly. I have seen some forget to clean or change the filter and they are either clogged with debris or get painted over heavily and they cant breath well.

The slanted mount engines use the same amount of oil as the standard horizontals, so if you put the engine flat level the oil line should be say midpoint in the threads of the fill hole. Too much in there and the crank and rod bottom get into the oil pretty deep and flung everywhere.
 
The breather looked fine, I disassembled it, cleaned it and added a new filter element. Ok, just to clarify, if I add oil to the engine setting flat on the bench and oil line is midpoint to the threads, I should be good to go once I install the motor on the Rupp frame approx at a 20 degree angle? Do not add oil once the engine is mounted at that angle? Sorry for the confusion on my part...., just want to make sure.
 
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