Tecumseh Engine Questions.

Hi to all of you,
Sorry i was not able to open an new thread with my engine, so I used this one,
I recently bought an AL-KO ride on 620, for personal use, and the engine is an Tecumseh VLV55, it was starting really bad, but i accepted the challenge, so therefor I'm here on the forum requesting advices.

1) I disassemble the engine, and I'm surprise to find that the combustion chamber is made from aluminum, without steel, which is not an pleasant surprise, further more, the cylinder walls are severely damaged, my plan is to bore the cylinder form 70mm to 73 mm and change the piston, with one from Honda, which is really cheap, about 10$ with the rings attached
Looking forward for your opinion, on my idea

BR
Mihai

As long as the distance between the face of the piston to the wrist pin is the same, I don’t see why there would be any issue

Hi
I'm just trying to understand, what if the distance is not the same ?

if is longer, but not long enough to hit the spark plug, or if is shorter, what then? does it really make such difference ?, the compression ratio is dictated by the amount of air dislocated by the movement of the piston, considering that the piston is bigger in diameter an bigger amount of air is compressed, I believe that an shorter piston should behave better.

Maybe someone from the forum has an honda 73mm piston and measure, for the tecumseh i will make the measurement and post it here

I made a new new topic for your posts so we're not posting in that old thread..

My biggest concern would be about the wrist pin diameter. If the Honda piston uses a smaller or bigger wrist pin than the Teccy, your connecting rod will not work.

If you knew someone with a milling machine you might (key word there, no idea if it would work) be able to either bore out the piston or con rod to fit whatever wrist pin fits better. But, it would be a lot of work and I don't know if you could get the tolerances close enough but it might be worth a shot.

@AllisKidD21 thanks, I wanted to create one by my own but I guess I don't have the rights for it.

So, you are correct, I already looked into this topic, and Honda uses 18mm wrist pin and Tecumseh uses 14mm pin, so 2 bushings are necessary for the Honda piston, my plan is to use the the connecting rod from Tecumseh, because there is no visible wear and it will be easier to make the adaptation,
Or do you believe that there are other solution for my problem (of course chip solution )

I wanted to share one picture but it cant, yet, I'm to new on forum

They’re is a frequently asked questions (FAQ) section for how to start a new thread and how to post pictures, give those a read to help navigate around the site.

As far as the compression ratio, if it does come flush with the top of the cylinder you will see a small gain in compression due to the bigger bore, like you said. I don’t have the time to crunch the EXACT numbers at the moment but if you have the measurements it’s easy enough. If the piston face does not come flush with the top of the cylinder you will lose a bit of compression, like you said. Depending on how far down it sits it may offset the bigger bore to be the same compression ratio, or it may end up lower compression than before. Higher compression is always better for power though, so ideally it will sit flush.

I thought about wrist pin diameter after I posted about pin to face distance, but you could do as you said and use the smaller pin with the bushing in the piston, do as @rustbucket garage said and bore out the connecting rod to accept the larger wrist pin. Does the connecting rod have enough material to bore out and retain similar strength as factory? If it looks big enough, that’s the route I’d go. If you did use the smaller pin with bushings in the piston, how do you plan on retaining them in the piston to keep them from scuffing the cylinder bore? Does the Honda piston have a provision for a snap ring/circlip?

What about the width of the connecting rod? Is the skirt of the piston wide enough to allow the connecting rod to line up with the bore for the wrist pin? Is it too wide to the point where it may need spacers?

Sorry if this post is overwhelming, just trying to think of everything here before you waste time or money on parts that may not work

The link to the how to post a pic in in my signature below!
:down: :down: :down: :down: :down: :down: :down:

So, i did some measurements, the Tecumseh piston has 27mm from the center of the pin till the face of the piston, the Honda piston (i have an 68 mm piston form an old GX160, I suppose the distance will be the same for an 73mm) has 24 mm, therefor the distance is 3mm smaller for Honda,
Considering the increase in diameter i guess the compression pressure should remain the same.
@ CraftsmanQuad19 The Tecumseh rod will allow to bore to 18 mm for the Honda pin, but the risk is to high, the outside edge is 21mm, if i bore for 18mm it remains an 1.5mm edge, and i consider to be to less, so i must use the 14mm pin form Tecumseh and bushing for Honda piston, I will try to upload an drawing for better

So, by honing i was able to reduce the scratches

Hope it works, without chaging the piston

Hi to all
It works but the start is still not acceptable
It takes up to 10 puls to start, i must mention that the carburator is brand new.
Any sugestions?

It sounds like one of two things.

Insufficient or low spark, so either points/condenser need to be replaced or the coil is on its way out.

Low compression- bad rings, valves need lapping.

Is the new Honda piston installed, or was this with the old Tecumseh piston?

Hope that helps.

Hi

The spark plug is brand new, and there is no condenser, on the circuit, only the coil, and the distance between the coil and the flywheel is set using an business card  

The low compression is most likely the issue, the piston is still the old Tecumseh and the rings are still the old one, for tecumseh i was not able to find on Romanian market, so I bought for Honda, for the 73mm piston, but I was unlucky the 73mm from Honda uses 2mm rings, and tecumseh uses 1.6mm rings, therefor I used the old rings, which have about 3mm opening

but after an discussion to a local company specialized on engine rectification, it seems i will change the entire engine, their statement is that the operation to bore for the new piston will be unsuccessful due to the material surface treatment which will be removed by the bore operation and the right way to do it is to bore larger then 73mm and press an steel cylinder for the new 73mm piston, but this operation will cost 150$ and i can simply buy an new engine for 200$,
I was looking for an Loncin LC1P70FC, what do you think?

I have ran engines way worse bore scratches then that. Engine is probably still usable. Thinking it is just a tuning problem. Look into ignition, move the coil closer to the flywheel to get a better spark. Check valves to make sure they are seating by seeing if they spin in the engine block by turning them with your hand, when not on a lobe. Seats might be worn and are not sealing

mihai.salajan wrote:

Hi

The spark plug is brand new, and there is no condenser, on the circuit, only the coil, and the distance between the coil and the flywheel is set using an business card  

The low compression is most likely the issue, the piston is still the old Tecumseh and the rings are still the old one, for tecumseh i was not able to find on Romanian market, so I bought for Honda, for the 73mm piston, but I was unlucky the 73mm from Honda uses 2mm rings, and tecumseh uses 1.6mm rings, therefor I used the old rings, which have about 3mm opening

but after an discussion to a local company specialized on engine rectification, it seems i will change the entire engine, their statement is that the operation to bore for the new piston will be unsuccessful due to the material surface treatment which will be removed by the bore operation and the right way to do it is to bore larger then 73mm and press an steel cylinder for the new 73mm piston, but this operation will cost 150$ and i can simply buy an new engine for 200$,
I was looking for an Loncin LC1P70FC, what do you think?

I think you’re right on the low compression, might try some tighter rings and see how that works. Your call though.

Also, if the remaining scratches still bother you, have you considered an oversized Honda piston? Might give you the needed bump to hone out the rest of the scratches.

prancstaman wrote:

I have ran engines way worse bore scratches then that. Engine is probably still usable. Thinking it is just a tuning problem. Look into ignition, move the coil closer to the flywheel to get a better spark. Check valves to make sure they are seating by seeing if they spin in the engine block by turning them with your hand, when not on a lobe. Seats might be worn and are not sealing

Thanks for your advices, when I was honing the cylinder walls I've also cleaned and lapped the valves, and the ignition coil is really close to the flywheel, also the spark plug is brand new, so I guess the rings are my actual problem.

Rustbucket Garage wrote:

I think you’re right on the low compression, might try some tighter rings and see how that works. Your call though.

Also, if the remaining scratches still bother you, have you considered an oversized Honda piston? Might give you the needed bump to hone out the rest of the scratches.

As i was already writing, the oversize piston is an expensive operation, in comparison with the engine price, so therefore i decided to purchase an new engine

I have put my eyes on an " Zongshen XP200A " is an 6.5HP, is cheap about 170$ on local market, the footpath is identical, it should be an easy replacement, and as an plus is uses an carburetor with choke, and not with primer, which I consider to be an better solution.