Hayter 21 - Help please

[Rayp 46]

My Hayter 21 is very difficult to start.  It has good compression and a good spark, but when it does run it performs a little 'lumpy' and the exhaust fumes are somewhat 'sooty'.  I am currently cleaning the fuel tank and carburettor, but can any one suggest any other possible causes for its difficult starting.  Also can anyone tel;l me where to buy Briggs & Stratton red engine paint or a near equivalent (preferably in a spray can).

 

 

[S1g 579]

Personally I'd reg rind the exhaust valve and replace the diaphragm.

[Wristpin 400]

Certainly good valve sealing and adjustment is the basis of a sweet running engine. Don't just do the exhaust, I've found that the thirty degree inlet vales on 5hp BS engines seem to suffer a bit and benefit as much from a re- seat  as much as the supposedly harder worked exhaust.

Quite often poor starting on 21s and Ospreys was down to nothing more technical than throttle cable adjustment not applying the choke  fully. Back in the day it did seem that the standard fit throttle control only had just enough throw to give both full choke and stop. Couple that with a bit of wear and slop in the pivot of the lever on the carburettor throttle plate and it was a choice of one ore the other but not both. We would often set them up for a reliable full choke and fit a handle bar mounted kill switch to look after stopping.

[S1g 579]

As a rule I allways do both valves when servicing any engine, however I guess I have got so used to people telling me that I'm wrong that valves cause fuel issues that I've developed the habit of only recommending the exhaust. Always do both reguardless of how good compression seems.

[Rayp 46]

Thank you both for your recommendations - I will follow these.

[Anglo Traction 1,016]

Hello Ray, Just to say that I fully agree with the advice offered re Valves etc, as I'm an advocate of pulling the head off of any engine I get irrespective of condition and give the Top End a good going over.  The result is very few issues with starting and running.

Only other thing to mention is that the 'Sooty' appearance of the Exhaust emission is usually caused by Over Rich Fuel settings, it will also retard your chances of an easier start.

The 'Book' says the INITIAL Needle Valve setting on a 5hp Pulsa Jet/Vacu Jet Carb is 1 1/2 turns from a gently closed position. It is further adjusted (finely) to obtain the best running setting.  This is assuming the Needle Valve Tapered end is not damaged or worn.  Check your Plug gap is 0.030".

Lastly, even if your Carb setting is correct, if  your Air Filter is tatty and clogged up, then your fuel mixture becomes Rich. Always worth replacing it and servicing it regularly. Let us know how you get on. 

Regards.

[Wristpin 400]

There is a very good manual "Small Engine Secrets and Solutions) written by John Carrow a BS MST and Technical Manager in Australia for many years. Unfortunately now out of print but worth searching for. 

This is a quote from the book and one of my favourites.  (boringly so !)

 

"Technicians who are valve critical will always have a better record of repair success than those who take a near enough approach"

 

A lot of time can be wasted fiddling around with carburettion and and ignition to no effect unless the valves are right.

 

 

[S1g 579]

1 hour ago, Wristpin said:

There is a very good manual "Small Engine Secrets and Solutions) written by John Carrow a BS MST and Technical Manager in Australia for many years. Unfortunately now out of print but worth searching for. 

This is a quote from the book and one of my favourites.  (boringly so !)

 

"Technicians who are valve critical will always have a better record of repair success than those who take a near enough approach"

 

A lot of time can be wasted fiddling around with carburettion and and ignition to no effect unless the valves are right.

 

 

Probably one of the truest statements that I've ever read. Years ago I gained a bit of a reputation locally as a Gx Honda guru, ( before all the Chinese stuff got about)people used to ask me what my secret was in sorting out so many problem engines and I said there was none, simply pop the head off,de coke, grind the valves in, new plug and air filter plus fresh fuel and then 99% of them would be sorted. It was rare that I had to delve deeper,usually took less than two hours from start to finish.

[Rayp 46]

Thanks for the advice - I'll look out for the Book and let you know the outcome of my efforts.

[Stormin 4,458]

A trick I use, but can only be applied to OHV engines after valves have been lapped in and re-assembled, is  to pour petrol down the ports. If any dampness appears then I re-do them. If petrol can't get through, neither will gases.

[Wristpin 400]

5 hours ago, Stormin said:

A trick I use, but can only be applied to OHV engines after valves have been lapped in and re-assembled, is  to pour petrol down the ports. If any dampness appears then I re-do them. If petrol can't get through, neither will gases.

Standard old school practice but not with petrol  - elf and safety. Paraffin , diesel or even water, but if valves are correctly lapped they will seal correctly. Only ever use the paste from the fine end of the tin; if that is not sufficient they need to be refaced and the seats cut. If the coarse paste is needed to recover a bad valve or seat the chances are that you will end up with a convex valve face and cupped seat. 

The days when cars needed a decoke every ten thousand miles and every village garage had refacing and seat cutting facilities are gone - as are the garages: so us small engine types have to seek out those who have the kit. A decent garden machinery workshop should have it as will vintage motor bike shops but otherwise it will be engine reconditoners who may turn up their noses at our sort of kit.

Edited March 28, 2017 by Wristpin
Typo!

[Rayp 46]

Stormin and Wristpin,  thanks again for your advice.

[Rayp 46]

Just to let you know I followed all your advice regrinding both valves, decoking the head, replacing the plug, diaphragm and gaskets. The mower now starts easily and as soon as the new belt and blades arrive I hope to put it to work.

[Stormin 4,458]