Brand new SC91 hard to start

[John Tennant 2Participant @johntennant2]

Hi

I have upgraded from an old HB61 to an SC91 in my 47" huntsman 31.  Naturally I’m expecting big things in terms of performance etc.  Problem is that the engine is proving a hard beast to fire up.  It seems to get stuck at TDC of which the scant instructions say is normal (eh??).  I have had it fire and pop at the exhaust and had the smell of this type of exhaust waste but not been able to actually run it up in my test tank (empty fish pond!) at the bottom of the garden that I fill and empty as required.  I’m using a 12V belt starter but it still jambs.  Have lossened the glow plug to lessen the compression but to no avail.  Any thoughts???

[Paul TParticipant @pault84577]

Hi John

Is the carb set to lean with to much air in the mixture?

Paul 

[John Tennant 2Participant @johntennant2]

Thanks for responding.  The needle valve I have turned 2.5 times out which I thought was kind of standard for starting.  Problem is I can’t turn the beast over to fire it up.  It only pops and stops jamming at TDC each time??

[Paul TParticipant @pault84577]

Hi John

A few questions spring to mind so I have listed them in no particular order.

Is this a brand new engine?

Has the head been skimmed to increase compression?

Is the crankshaft straight?

What condition are the crankshaft bearings in?

Are you using the correct fuel mixture?

Don’t you just hate these little engines sometimes  I think that they are more trouble than they are worth.

Paul

[John Tennant 2Participant @johntennant2]

Yes, the engine is brand new out of the box.  First time ever fed with fuel and probably turned in anger.

Standard head I assume not skimmed as new

I hope the crank is straight!

The bearings one would assume is as new as the rest

Using the same fuel as in the last engine although it is over a year old but never gave any problems before?

I was going to buy a strimmer engine!!!

[John Tennant 2Participant @johntennant2]

Here’s a picture if it attaches??

  

[ashley needhamParticipant @ashleyneedham69188]

Hi. I would straightaway try some new fuel. Also you can get blends specifically to run in new motors? This sort of stuff goes off very quickly, just like petrol.The volatile stuff evaporates and you get left with only the oil content. I certainly wouldnt try to use year-old petrol in my motorbike after a layup!   Ashley

[Paul TParticipant @pault84577]

Hi John

I would agree with Ashley about trying new fuel I would also run a little castor oil through the cylinder (turn by hand with plug out) just to get a little lubricant around all the important little places.

I had a similar problem with a super tiger engine oddly enough in a 4ft Huntsman and after changing most of the parts I found out that the con rod was slightly bent, thus it was shorter in the sleeve and always stopped with a click at TDC.

So I have changed over to strimmer engines

Paul

[Rich FordhamParticipant @richfordham89999]

I had the same with a new ASP 61 (very similar, but higher compression than the SC’s).
It broke the crank on the first try of starting, it was so tight. It had to go back to the shop.
It still is very tight when cold, a dynotron on a good battery is the only thing that will turn it over.
I found that the best setting is with the needle at about 1 1/2 turns, even though the manual says 2 1/2.
Try loosening the plug when starting, and putting a couple of drops of 3 in 1 on the piston before you try starting just to make sure you don’t do too much damage.
I run Formula Irvine 10% fuel as it is nice and oily.

Hope this helps.

[John Tennant 2Participant @johntennant2]

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