Welcome, Guest. Please Login or Register
vintagesnowmobile.com
09/23/17 at 11:26am
 
  Art's Parts Home Jim Solberg's Vintage Snowmobiles Classifieds Bruts on Facebook Brut Info Show Pics SearchLoginRegisterHelp Gene's Salvage  
 
Pages: 1
Send Topic Print
Need help with '72 Moto-Ski Tillotson issue (Read 622 times)
lucky0_7
50 or less
*
Offline



Posts: 2
Embrun, ON, Canada
Gender: male
Show the link to this post Need help with '72 Moto-Ski Tillotson issue
01/28/17 at 8:22pm
 
I've posted this on another forum so I'll just put up my initial post and my own subsequent personal replies. I've you've seen this elsewhere disregard. If you haven't any thoughts would be appreciated.

Initial Post:

So I'm having a few issues getting the old girl running right. It's a Hirth 194r 338cc with a Tillotson HD carb on it. My main problem at this point is that I can't get it to idle unless I turn the low speed mixture screw way out. If the low speed screw is out 1 to 1 1/2 turns when I completely let off the throttle it will idle for 8 or 10 seconds then stall. It's starving for fuel at idle but she runs like a dream other than that which I find bizarre. Lots of power and running mint according to the spark plug

Now if I open my low speed needle out 2 1/4 to 2 1/2 turns it'll sit there and idle at 1750 rpm all day long but driving around it seems to load up when I let off the throttle too long and try to accelerate again. Pull the plug after it's idled a bit and it's moist/shiny.

I guess my first question would be is it normal for the low speed needle to be out that far in order to get it to idle? If not, what would cause it to have to be out that far? Pop off pressure too high? But wouldn't that affect high speed operation as well?

Here is a list of the recent work that I've done so far this fall and last year. Might aid in figuring things out.

- Fuel tank drained and cleaned, check valve in tank is good.
- All new fuel lines
- Block pressure/vacuum tested and holds air without drop
- New mag side crank seal (after pressure test but it was weeping a little and I was already in there)
- New exhaust gaskets
- New gaskets between carb and block
- Winderosa carb kit put in... no other options (diaphragms, welch plugs, mixture needle o rings)
- Put needle and seat from the kit in recently to see what would happen.
- New old OEM steel high speed mixture screw (previous brass one was warped)

Next thing I may try is going back to the old needle and seat see what happens. And I'm in the process of rigging something up to test my pop off pressure. But both are just a shot in the dark I guess as I don't know what would cause that idle issue.


Next post of value:

Alright so I played around with it a bunch and ended up putting in an old captured needle from an scrap carb and a forked fulcrum arm. Now she'll idle with the low speed mix at 1.5 turns out all of a sudden. Haven't played with it too much after I got it going since it was getting dark. Going to check how fast its idling and try to adjust everything properly later today hopefully.

When I was playing around with it after I had put everything back together I wasn't noticing much of a change when adjusting the low mix screw. If I lean it out I don't get that usual rpm increase that confirms you're at a point where the mix is starting to lean out. Just seems to run a little rough for a couple seconds then stall out. Hard to notice minor changes in the way its running when trying to tune those darn hirths since they rattle and buck so much.

Never had this many issued getting a darn carb working right.

Last one (no replies to this one yet):

Well I fiddled around with it yesterday and it's idling great now. Starts with the choke as it should, which it wasn't doing consistently before. Takes off great from a dead stop... BUT now I can't get it to wind out like it used to at WOT. If I keep the throttle a little short of full she pulls consistently, but if I hold it wide open it doesn't wanna go get that last bit of rpm. Feels as though it's pulling an extra 100 lbs all sudden, and if I hold it open long enough it'll eventually spool up a little more and sound better, but not as good as it used to. High speed needle adjustments seems to make it worst or change nothing no matter which way I go. Plug color is beautiful, just a tad on the lean side after my last adjustment.

When I lay off the throttle for a turn I can't get back on her to spin the track and drift through like I used to either, bogs a little when I get back on it.

I think I might just chalk it up to the weather for now considering temps were hovering around 32 last night when I was playing around.


Anyways, that's the progression, I know it may seem a little odd but I'd rather put in more info than less. So ... anyone got any ideas on how to get this thing running right?

Back to top
 
  
View Profile   IP Logged
restomajic
Forum Moderator
*****
Offline

Vintage Rules!
Modern sleds DROOL
!!

Posts: 2722
Central NY
Show the link to this post Re: Need help with '72 Moto-Ski Tillotson issue
Reply #1 - 01/29/17 at 8:40am
 
So now that you are happy with the low speed and idle, it seems lazy on the top end and H adjustments don't seem to make a difference?

Have you tried any H settings that would be different than the base setting even if you are getting uncomfortably low or outrageously high?

What is the general condition of the carb itself? Have you inspected the throttle plate shaft and the holes that it pivots in?
Back to top
 
  

Restomajic
Visit my Ski Whiz site at: http://vintagesleds.com/skiwhizrescue/
skiwhizrescue1@yahoo.com
View Profile WWW   IP Logged
lucky0_7
50 or less
*
Offline



Posts: 2
Embrun, ON, Canada
Gender: male
Show the link to this post Re: Need help with '72 Moto-Ski Tillotson issue
Reply #2 - 01/29/17 at 7:58pm
 
Carb is in good shape. Perfectly clean and the throttle shaft is in there nice and tight. Opens and closes freely so I know it's not an air flow problem.

I have played with the high speed screw opening it up way too much until it really starts faltering. On lean side I'm a bit of a chicken because I don't want to blow it up but I've gone down to a little under 3/4 of a turn and it didn't solve the problem. I pulled the plug and was able to confirm that it was running pretty lean when I did that. So I opened it back up to where I was getting a nice looking plug and left it for the night. Rode it a little more and problem stayed but everything remained constant.

The plug looks perfect right now if not a little on the lean side after running her hard for a bit. That's what's really throwing me off at this point.
Back to top
 
  
View Profile   IP Logged
Pages: 1
Send Topic Print