Some Advice Please - What Would You Do?

[nheather]

Last year I bought my son a used Hyper 28 from this forum - great package but the Mach 28 engine is very tempremental - well tuned it runs well but takes a lot of attention between each run as it doesn't hold tune well. Tried everything to resolve this but no go and researching, this seems to be a common feature of Mach 28 engines. It's frustrating enough if I'm with my son but it would be too much for him to do on his own.

Anyway, I decided to replace it with a 21 (which I have read are a lot better) and decided it must be a Hobao because I have a Rotostart with a Hobao back plate (I assume different makes would require different backplates - is this true?).

But needs to be on a budget becuase this is really only a toy.

After looking here with no joy I bought a Hyper 21 Pro 8 port from evilbay.

It was advertised as good performance, runs well, good compression, only 2 gallons.

What I received has done way more that 2 gallons. The pullstart (although I don't need it) is showing loads of wear, scuffing, ingrained dirt. The carb is also showing a load of wear with scuff on the intake and the blacking on the barrel has been warn away - also the needle screw heads show some chewing. When I removed the pullstart, I noticed that the screw threads in the backplate are warn (perhaps has ssen several pullstarts)

Not sure about the body, it's reasonably clean but I would need to take apart to inspect piston and liner which I'm not prepared to do.

I have tried running it - it took quite a bit to start initially because the settings were way off 20% or factory default. When I did get it started it seems to run okay.

I have raised these issues with the seller. At first he stuck to his story, but gradually he admited that he had bought the engine from a friend and that the engine could have seen a lot more action than advertised.

Now the seller is a decent chap and has offered to accept the return and refund the purcahse price and postage costs.

So what would you do - it runs, it was reasonably cheap (

[hazza1304]

Send it back. 100% no doubt

No point keeping it as it might give up after say half a litre and then you would have to buy another one

[kirkbride]

Yeah send it back it could be on its last legs and give up on you anytime, and youll be back to square 1.

[nheather]

Thanks for my replies - you have pretty much echoed my feelings anyway.

Next question - where to go next.

Do I keep perservering with the Mach 28?

OR

Do I go for something else?

If something else then do I go new or old?

And if I want to reuse my RotoStart does this mean I have to stick with Hobao\Mach or are all backplates pretty much standard. The rotostart I have is this one

http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=25032

Cheers,

Nigel

[jamodabest]

http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=28508

I bought that for my hyper 7 and its a great easy to use engine, it wudnt let you down.

[maiden939]

Thanks for my replies - you have pretty much echoed my feelings anyway.

Next question - where to go next.

Do I keep perservering with the Mach 28?

OR

Do I go for something else?

If something else then do I go new or old?

And if I want to reuse my RotoStart does this mean I have to stick with Hobao\Mach or are all backplates pretty much standard. The rotostart I have is this one

http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=25032

Cheers,

Nigel

mach 28 fantastic engine , main causes of not holding tune are air leaks, bottom of cooling head, back plate and carb neck where its bolted to engine all really simple to seal

[nheather]

mach 28 fantastic engine , main causes of not holding tune are air leaks, bottom of cooling head, back plate and carb neck where its bolted to engine all really simple to seal

Must admit that air leaks were my first thought and I changed all the fuel pipes and the o-rings.

Is there a way for checking for air leaks?

If I do find one, how do you go about selaing it?

Cheers,

Nigel

[TerrorTrooper]

i would definately send it back.

Its likely seen far more action than advertised, if its needles were way out it could have been run massively lean whitch will likely lead to unseen problems with the con-rod and piston.

Not to mention a million other problems that can happen with 2nd and 3rd hand fleabay engines.

one more thing.

But needs to be on a budget becuase this is really only a toy.

Tesco sell toy RC cars, these are hobby grade.

The same way as fishing rods and equipment arnt toys, but you can buy toy ones.

[Just Chris]

Must admit that air leaks were my first thought and I changed all the fuel pipes and the o-rings.

Is there a way for checking for air leaks?

If I do find one, how do you go about selaing it?

Cheers,

Nigel

Keep mach (you know the engine) go to pinned threads and seal engine then reset to factory settings and start again (but with a sealed engine)

Keep changing engines is not the answer ( iknow had 3 for my hyper) but now things are a lot better. Hope this helps.

[maiden939]

Must admit that air leaks were my first thought and I changed all the fuel pipes and the o-rings.

Is there a way for checking for air leaks?

If I do find one, how do you go about selaing it?

Cheers,

Nigel

theres a guide in the tutorials section on here to show you the way , just a good automotive sealant is fine

[Bash it]

Must admit that air leaks were my first thought and I changed all the fuel pipes and the o-rings.

Is there a way for checking for air leaks?

If I do find one, how do you go about selaing it?

Cheers,

Nigel

brush soapy water over the suspect areas

with a bit of fuel line connected to the fuel inlet blow down it at the same time put finger or thumb over air intake (the carb) and another over the exhaust outlet directly on the engine not the pipe. any bubbles there is your air leak

to seal it you can use some sort of high temp liquid gasket sealant that you can get from car spares for eg there may be better sealants about see what others say

if it is leaking from the needles use a small amount of green slime by team associated

Edited April 3, 2010 by Bash it

[nheather]

one more thing.

nheather, on 03 April 2010 - 04:51 PM, said:

But needs to be on a budget becuase this is really only a toy.

Tesco sell toy RC cars, these are hobby grade.

Yes, I didn't mean it quite like that. I fly nitro helicopters so I know full well that you get what you pay for. What I meant is that my son just uses it to mess around in the park or common ground - he isn't into racing so he doesn't need the best and it won't be heavily used.

So I was looking for a good quality 2nd hand engine rather than paying £100+ for a new one.

Cheers,

Nigel

Edited April 3, 2010 by nheather

[Just Chris]

You will know yourself (from helicopters) to get a 2nd hand engine in good nick is quite rare (only my opinion) why sell a good engine.

If you go down the new route there are engines around for under a

[nheather]

Many thanks for the support. Here is what I've decided to do with your advice

1 - Return the evilbay engine for refund

2 - Work on the Mach 28, especially looking at the sealing

3 - If no luck then buy a new engine - probably a Picco - I see they do one with a rotostart backplate, although out of stock at the moment.

Big Question though.

I've looked through the Pinned Threads and done a search for 'engine sealing' but I can't find any of the threads that the replies have suggested I look at. So I would really appreciate it if someone could provide an actual link\links to the thread\s I should be looking at.

Many thanks,

Nigel

[SmugR]

click

[nheather]

Many thanks that is great.

Few more questions

1 - what is the slime they talk about for the needles.

2 - Do you ever both sealing the head or do you assume that the brass\aluminimum gaskets will be good enough.

3 - Is the high temp sealent specific to model cars or do you just use stuff from Halfords

Cheers,

Nigel

[Just Chris]

Many thanks that is great.

Few more questions

1 - what is the slime they talk about for the needles.

2 - Do you ever both sealing the head or do you assume that the brass\aluminimum gaskets will be good enough.

3 - Is the high temp sealent specific to model cars or do you just use stuff from Halfords

Cheers,

Nigel

Green slime by associated

http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=17177

I use copper gasket sealent from halfords (about a fiver) ask at service bay

[nheather]

Many thanks

I use copper gasket sealent from halfords (about a fiver) ask at service bay

I assume this is for the backplate etc.

And the green slime is for the needles.

Is that right?

Cheers,

Nigel