The Old Lawnmower Club
Collection, Preservation and Display of Old Lawn Mowers

Suffolk Colt 75cc Recondition or not?

peternsomerset

Hi,

I bought a very rusty Colt for the engine as my 17inch Super Punch was not running well.

I now have the 17 inch running OK but its heavy and was thinking of a restoration as its so much lighter!

The engine runs OK but smoke a lot and would appreciate some advice if its worth continuing!

It has good compression and have removed the head,  the plug, piston and head were very oily,  in particular from around the inlet valve.  Cleaned top of piston and rotated crank,  the has no sideways movement and the bore seems perfect.

I had already checked the crankcase valve and it was OK and there was very little oil in the chamber (where the valve rods/guides are located).

There is a lot of carbon between the 2 valves and I will need to remove them a give it a de-coke but is it likely the valve guides are the problem and its not worth proceeding or its only a matter of replacing the rings!?

Thanks  

 

 

 

Forums

Mowing Wurzel Sun, 25/08/2024

Good Day, 

Thank you for the post, I hope somebody more technical with Suffolk can advise.

As always, please add on some photos.

The fundamental question would be; how much money and time you wish to put into the project?

We all love our mowers and being obsessive collectors, pour lots of money and time into them!

Like all projects, obtaining donor machines for spares is certainly a must.

Engine wise; I recall the Colt engine is 75cc and the Super Punch is a 98cc unit,  so naturally you cannot fit a Colt to a Punch as would be under-powered.

Regarding smoking, as noted, cylinder and ring condition and valve guides are the main causes for smoking, On a separate ,mechanical appraisal issue, I would also inspect the main bearing shells for lift.    

 

 

 

peternsomerset Mon, 26/08/2024

Hi,

A picture of the head is attached for info.

The bore seems quite good with no scores,  i cleaned the piston and there iis no sideways movement,  the exhaust valve also ha no movement but there is some on the inlet, .  when I first removed the head there was fresh oil coming out from it across to the exhaust valve.

The engine runs first time and had quite a lot of compression BUT smokes a lot and has oil coming out of the exhaust box "slot"!!

I assume its the valve stem/guide,  which is more likely and is it a write off if the guide is worn?

FYI I have a very old Punch 17inch with split serated rear roller with a 75cc engine running under powered for more than 24 years,  and I understood these engines were initially on the mowers.

Any comments/advice welcomed before further dismantling or taking it to the Tip!

Thanks

Suffolk Colt Head Removedbb

hanks

Mowing Wurzel Tue, 27/08/2024

I'm sure somebody on the Forum will have technical info. on Suffolk Lawnmowers;   For checking on the said issues of valve guide tolerances, valve guide inserts, Ring gap reject sizes, etc..

 

peternsomerset Mon, 30/09/2024

I have to make a decision soon and have noticed the cylinder adjusters are virtually screwed hard down and the its only just making contact with bottom he blade!

Before taking to the tip/giving it away,  can any body tell me what a good cylinder blade width should be for a Colt?

I have just measured mine and its about 0.87 to 8.8 inches wide.

FWIW I have tried to move the cylinder up and down with the adjuster slack and there is no movement so I assume the bearings are OK.

Thanks