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SH P6-28 Pro Spec with severely aggravating problem

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P

PiGdOg

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:whhooo:

I am only new to the RC world and I have an SH P6-28 Pro Spec with severely a aggravating problem which I think is probably carby related

The engine is in my 1/8 off road buggy.

I run Nitro-X SSS fuel which is good quality fuel here in Australia and it is 25% nitro 11% synthetic oil


Problem is that I can't manage to get it to tune correctly. It will run, no problems at top end, I can tune that, then as soon as I touch my screwdriver onto the LSN it will idle lower and then stalls.

I thought it was the O ring on the LSN so I replaced it 3 times but still does exactly the same thing.

It is like the slide is worn and if I touch it then it moves slightly and changes the needle or something??

I ensured that the LSN and HSN can't move.

The engine is about 2-3 years old but hasnt had much fuel through it, and it has been stored with after run oil.

I have set the idle a touch higher so that the clutch is almost grabbing.

When I removed the carby and stripped it I noted that there was like a stain or wear patch on the slide, the needle looked in good condition.

The motor has great compression, even when hot.

After rebuilding and sealing the carby I began with the factory settings (3 full turns on the HSN and LSN) but no matter what I have tried it just wont idle properly.

Temps are good (usually between 98c and 110c depening on the day)

I live in mid north Queensland so its pretty warm and a bit tropical here so I use the #8 glowplug

I a replaced my tank and fuel lines because I thought that they may have been a problem.


Because of this problem I have rebuilt the carby with new Orings and totally sealed it, including full sealing of the motor with HighTemp RTV and I also completely sealed the rubber boot over the end of the slide but this did not stop the problem......


Any advice??

Is it just these carbys? If so then is there a replacement which is less problematic?

Looking forward to hearing back from someone.

Regards,
Andy,
Australia
 
May i suggest you try a different fuel as a comparison ? if you do not get the same problem, then you know what it is. Also, try an alternative plug.

One other thing, was that temp you mention the weather temp or engine temp ?
 
Hi, that is engine temp.

I tried another fuel, it is 20% nitro, 25% castor and 5% synthetic

I also tried the#3 glowplug.
 
When you set the idle, did you do it via the screw on the carb or the transmitter trim?

If you did it using the carb screw, what does the engine do when you apply full brake from neutral? Does it stall or does the idle change at all?

It does sound odd though.
 
olds97_lss said:
When you set the idle, did you do it via the screw on the carb or the transmitter trim?

If you did it using the carb screw, what does the engine do when you apply full brake from neutral? Does it stall or does the idle change at all?

It does sound odd though.
Click to expand...

Hi, I use the carby throttle stop screw.

When I apply full brake it makes the engine stall.

I have even opened the idle screw until the clutch is almost grabbing and it still makes the engine die when brakes applied.


I suspect that the carby slide has a problem because even if I have the servo rod disconnected and I touch the end of the slide it will still stall. I have even had the engine reving fast enough to engage the clutch and it will still stall if I touch it.

At the moment I am tempted to just order a new carby and see how that goes because I have stripped and cleaned the carby 3 times, cleaned with compressed air, sealed everything on the motor and carby, replaced all the Orings and seals on the carby 3 times, and it still does it.

Man it really is peeing me off.
 
Yeah... that's very strange. Not sure what I'd do if I were in your boat. I think I'd be looking for an alternative carb from a different mfr. Avoid the issue altogether.
 
olds97_lss said:
Yeah... that's very strange. Not sure what I'd do if I were in your boat. I think I'd be looking for an alternative carb from a different mfr. Avoid the issue altogether.
Click to expand...

What other manufacturers carbys are good? What else would fit straight up to my SH P6-28 ProSpec I've been working on cars etc for 30 years but I'm only new to the RC stuff.
 
Tear the engine apart and inspect the bearings for play. It sounds like you could possibly have a bad front bearing.
Front bearings don't last long, 1-2 gallons of fuel and they are toast. They develop slop and let the crank wobble and also excess air comes through the bearing seals causing the engine to be impossible to set on the LSN.
 
Any of the LRP, XTM, Dynamite .21-.28 carbs will work.
 
Scrogg said:
Tear the engine apart and inspect the bearings for play. It sounds like you could possibly have a bad front bearing.
Front bearings don't last long, 1-2 gallons of fuel and they are toast. They develop slop and let the crank wobble and also excess air comes through the bearing seals causing the engine to be impossible to set on the LSN.
Click to expand...

Hey thanks heaps for your suggestion Scrogg. :first_place: :goodpost:

I ripped the motor apart tonight after work and discovered some weird sh!t... :whhooo:

The bore and piston look good.
I have not been able to get the conrod off the crank but I looked through the carby hole and the exhaust hole.

When the piston is at top dead centre it feels like it has a notch in it which sort of stops it at TDC. I'm not sure if this is normal or not?? :ponder2:

I stripped the clutch off and I can definitely feel movement on the crank when I grab the front and move it up and down, and if I stick the piston at BDC and move the crank I can feel the piston move ever so slightly up and down in the bore.

Ok, so now I am almost certain that it is bearings, :juggle: so how do I go about getting the conrod off the crank??? :ponder2: :OMG: Do I need to remove the piston sleeve to allow the piston to move further or what?


I really wantta get this 28 going good so that I dont have to use the 21 in th :buggy1: :redbuggy: :Australia:
 
Yes you have to get the sleeve out. Insert two plastic cable ties thru the exhaust port of the engine and rotate the piston up and the sleeve should come up a bit.
Do not use pliers to get the sleeve out.
Once the lip of the sleeve comes up a few mm's, you can gently use two flathead screwdrivers to pry up the sleeve. Be careful not to scratch the soft brass exterior of the sleeve.
Then rotate the piston to the top, turn the engine upside down and gently wiggle the rod off the crank. Pay close attention to the rod and piston orientation so that you do not install it backwards later.
On to the bearings...once you have everything off the engine preheat your oven to 250F.
Throw the naked block in the oven for 10 minutes..Then use a 3/8" drive socket extension to drive out the front bearing with a light hammer.
The wobble you described is enough to cause your tuning issue. My Picco is doing the same thing, when I tore it down the bearings and the rod were bad.
 
Thank you so much Scrogg!!! The problem is definitely bearing related.

Took the bearings to my local bearing shoppe today and they said "yep, they are definately worn"

I got prices on standard metal bearings and ceramics but I was shocked :whhooo::seeing_stars:that they were AU$260 for 2 bearings.

I'm now looking for a reliable supplier in the US as I'm certain that they can be had for alot less , even with currency conversion fees.

The bearings I need are 13x24x6mm for the rear crank bearing (it can be an open bearing) and 7x19x6mm for the front bearing (has to be sealed)

I found a site but I'm not sure about the quality of the bearings. I've been reading up about ABEC ratings and from what I can see it is basically the higher the better, but this company only has ABEC 1's which are a standard bearing.

Does anyone know of a supplier of quality ceramics??
:sick: :burp: :juggle:
 
Scrogg said:
Don't waste your money on ceramic bearings for a used engine....
Click to expand...

Don't waste money on ceramic bearings for a used engine ?? what a load of BS !!!!

Besides which, thats like saying "Don't waste money on ceramic bearings for a used rig".

If the guy wants ceramic bearings, it HIS choice, NOT ours !! we only have "Opinions", not the final decision !!

*** EDITED !!! ***
 
Last edited:
What's your problem?
He is not installing a new piston and sleeve and rod. That's why I said not to spend a lot of money on bearings..SH engines generally loose compression around 5 gallons.
I did link him to an affordable ceramic main bearing and a good steel front bearing BTW.
Besides...who diagnosed the problem....cough, cough?
Chill with the "WTF's" and reread the thread!
 
My Problem ? nothing,i was merely pointing out that it's the guys choice to fit ceramic bearings, or not, as the case may be.
 
Last edited:
Scrogg said:
Don't waste your money on ceramic bearings for a used engine... that engine will not last for too much longer anyways.
Well.... I take that back. Boca has them cheap for your engine.
http://www.bocabearings.com/main1.aspx?p=product&id=9653&n=*ENK-005C-LP
OR
Since you know the size, hit E-Bay.
Click to expand...

Thanks Scrogg, I've looked on the bay and nothing :O Well I seen that link to Boca so I think that I will get them from there as their price is less than half what I was quoted for ONE bearing from my local bearing supplier here in Australia

I just emailed boca to ask freight costs before I commit though.

Thanks everyone for the suggestions and help.

Please dont get upset at others posts though, these forums are way too helpful to worry about fighting!!! Either play RC's more of have another drink lol!

Cheers!
:banana-mario: :drink: :bowtothercnt: :buggy1:
 

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