I've been working on this Savage 4.6 for 3 weeks and I can't get it running, help!

[Freezectrl]

So I've decided to get my Savage 4.6 running again and it's been nothing but problems

At first, the engine wouldn't crank with the roto start, so I toke it apart and found the starting spring was broken, switched it out no problem there
While taking the engine apart I decide to seal it using RTV silicone copper, again no problem, pretty straight forward

Got it back together, and it is impossible to start, I got it once in like thirty minutes but it was running super poorly, open throttle barely moves it forward then it dies right away. Found that my fuel tank was leaky so replaced the o rings, it now no longer leaks.

Things I have tried up to this point
New fuel
new glow plug
new glow driver
new different glow plug
new fuel lines
having the carb needles at stock
changing the carb needle slightly
changing out the exhaust manifold gasket

After trying to start it today I think I blew the spring again, it barely cranks now so that's another 10$ gone

What else can I try at this point?
The only other thing that I've thought of is the o ring for the high speed needle looks pretty worn as I was taking it apart to add green slime

What am I missing?

 

[Racer 1966]

Did you pull all of the needles out of the carb and make sure the passages are cleaned? The o-ring may cause tuning issues but shouldn't prevent it from starting.

Did you physically verify the glow plug/driver is operating good before putting the plug in the engine?

Clarify "it barely cranks". Do you mean the engine isn't physically rotating - that = cranks or are you saying it isn't starting when it cranks - that = not firing. If it isn't cranking but the roto-start is spinning, try cleaning the one-way bearing.

If the carb is clean,the plug/igniter is working and it is cranking, try priming it with a little fuel directly in the glow plug hole. Turn the engine over by hand(with the flywheel) a couple of turns before installing the plug and trying to start it. You do not want too much fuel so as to hydro-lock the engine. I am assuming the engine has good compression/pinch.

 

[Freezectrl]

Did you pull all of the needles out of the carb and make sure the passages are cleaned? The o-ring may cause tuning issues but shouldn't prevent it from starting.

Did you physically verify the glow plug/driver is operating good before putting the plug in the engine?

Clarify "it barely cranks". Do you mean the engine isn't physically rotating - that = cranks or are you saying it isn't starting when it cranks - that = not firing. If it isn't cranking but the roto-start is spinning, try cleaning the one-way bearing.

If the carb is clean,the plug/igniter is working and it is cranking, try priming it with a little fuel directly in the glow plug hole. Turn the engine over by hand(with the flywheel) a couple of turns before installing the plug and trying to start it. You do not want too much fuel so as to hydro-lock the engine. I am assuming the engine has good compression/pinch.

I pulled out all the needles when I greased them up with greens lime while sealing the engine, they looked clean at the time

I checked the glow plug and driver and it glows, though after charging it some more today and just checking it again, it does seem to glow brighter then before now, even though I charged it for 20 hours yesterday.

Barely cranks is the engine is not physically rotating with the drill start, I have an older F4.6 that has the nitro start, no OWB just direct to the starting shaft

I did try the fuel directly into the carb a few times, it does start then dies right after. Engine has good compression

 

[Rolex]

I did try the fuel directly into the carb a few times, it does start then dies right after.

That means it will run and you have a carb issue. You know it's not compression or the glow plug. It also sounds like you need to remove the OWB and clean it thoroughly. Also clean the shaft.

 

[Freezectrl]

That means it will run and you have a carb issue. You know it's not compression or the glow plug. It also sounds like you need to remove the OWB and clean it thoroughly. Also clean the shaft.

Ok thanks! what I should look for in the carb when I check it, would it be something clogging it?
My f4.6 is an older version with nitro start, you spin directly into the back of the engine with a hex driver, no OWB
The starting spring has broken before, it got like twisted somehow and no longer pushs the starting pin out to make contact with the back plate

 

[cbaker65]

Ok thanks! what I should look for in the carb when I check it, would it be something clogging it?
My f4.6 is an older version with nitro start, you spin directly into the back of the engine with a hex driver, no OWB
The starting spring has broken before, it got like twisted somehow and no longer pushs the starting pin out to make contact with the back plate

If it is a composite type of carb. ,most likely ,it is junk!.....

 

[Freezectrl]

If it is a composite type of carb. ,most likely ,it is junk!.....

ah dang, it definitely is
Honestly I've contemplated buying a new engine at this point with how much trouble this thing has given me
If the spring breaks again I might just do
Spending 20$ on 2 tiny little springs feels really bad

 

[cbaker65]

ah dang, it definitely is
Honestly I've contemplated buying a new engine at this point with how much trouble this thing has given me
If the spring breaks again I might just do
Spending 20$ on 2 tiny little springs feels really bad

The composite carbs has a pressed on aluminum piece ,some are for the Mix meter needle ,in time ,that
aluminum housing that is pressed on to the plastic starts to leak ,creating air leak an causing the engines
tune to be lost!

I have a 5.9 engine that does that ,so to get it to run ,I have to smear silicone over the whole housing.
I also had a Ofna hyper 21 engine do the same ,but changed the carb over to a all aluminum body carb
from a Thunder tiger engine ,I have a extra aluminum carb that I need to see if it will fit the 5.9 Hpi engines
throat ,if it does ,I will be happy!....

Composite carbs should not exist!.....

 

[D3MON]

personally, i have not had any issues with composite carbs, though i have seen my fair share of people who have had issues.
if possible can you post a video of it trying to start? and also of when it does start when you put fuel into the glow plug hole?
what are the needle settings at? factory? or something else?
factory will be very rich, but it should at least run.
Idle gap~1mm
LSN- Flush
HSN - Flush

 

[Racer 1966]

Unless someone put an eliminator kit on it (may explain the easily broken springs) there is a OWB bearing
inside the motor. A bad carb can make finish tuning a pain but it should start and stay running.

The needles "looking clean" doesn't meant the passages are open. Did you spray some carb or brake cleaner or compressed air in the passages before putting the needles back in? Do you have the fuel lines routed correctly from the tank? Try leaving the fuel line loose at the carb, plug the exhaust and crank it. Does fuel flow out of the hose?

Hang in there a little longer, I don't think a new motor is needed yet. A video as mentioned may help us help you too. Sometimes these things a just a witch.

 

[D3MON]

+1 to the points above, also make sure to use non-chlorinated brake cleaner.
also if your OWB is slipping, you can clean it. hose it out with brake cleaner, then insert an end to a paper towl or rag, and spin the owb both ways, it will leave the debris on the rag that way, then rinse one more time.
when really rich, lots of oil will seep through the brass bushing in the backplate and will over oil the OWB causing it to slip.

also if it no longer works to clean out the OWB, you can get some really fine 400Grit sandpaper and lightly SCUFF, you are no sanding, just scuffing, the starter shaft the OWB rides on.

 

[Rolex]

Some useful info here:

https://www.rctalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/

 

[Freezectrl]

So I toke out the engine today to replace the starting spring, and to my surprise the starting spring was not broken! It was the hex thing grabbing on to the starting shaft that has slipped, causing the shaft not to be able to turn. This model definitely doesn't have a OWB, it's an old model of HPI called nitro start which has a hex thing grabbing directly on the starting shaft and you can turn it with a hex driver, I'll link a photo of the manual here. It's z721 in the manual, the thing that was slipping.

There was a lot of oil on the starting shaft (which I'm guessing causes the slipping) and the whole back plate, it looks like it came from the exhaust? Would it still be from the brass bushing on the back plate? I think I made a pretty good seal with RTV copper.

Can the exhaust manifold seal between the manifold and the exhaust port not sealing well cause fuel delivery problems? How does one check the seal on that? I changed out the old one because it had a giant crack on it but no one had the HPI one, so I bought a generic one from venom. From comparison it looked like it was close enough

I also cleaned out the carb today and it looked pretty clean, the o ring on the high speed needle has now broken so I'll have to get another one, it was flaking a little before but I guess me taking it out again broke it.

 

[D3MON]

a severe leak from the exhaust manifold can absolutely cause fuel delivery issues, that is where the engine gives pressure to pressurize the fuel tank to deliver fuel to the carb.

Z721 looks to be a grub screw, how the starter in these models work is a the little pin with a spring (1433) in the crankshaft nub grabs an indent that is tapered one way so it can overrun the starter shaft when the engine is spinning faster than the starter mechanism.

the brass bushing is designed to leak a little bit of fuel into the backplate to lube the OWB, it is not sealed tight. typically there is a OWB, but in your case they did away with taht and used a more direct drive much similar to the Losi Mach .26 line. it does look like if you wanted, you can get a new starter shaft in place of 15136 and convert to pull start.
https://www.ebay.com/itm/HPI-1-8-Tr...LATE-ONE-WAY-STARTER-SHAFT-carb-/401840693815

the o-ring on the HSN breaking like that leads me to believe it was also causing a massive air leak as it was most likely hard and brittle and no longer sealing against the housing.

 

[Racer 1966]

I have had issue with some exhaust seals on several engines. Some are too thin and do not seal properly. I had this issue until I found a good supplier when I was making and selling big block pipe adapters for the Revo 3.3 engines.

I researched a little on your starter and I think I am up to speed with you on it. If I saw it correctly then as you said there is no OWB. The starter shaft(15136) has 2 flats and the 2 set screws(Z721) lock the starter hex to the starter shaft. So it relies solely on the spring and pin for cranking the engine -correct?
So if you have slippage when cranking, either your set screws are loose/worn, the the spring/pin is sticking /not functioning or the end of the pin or edge of the lock groove in the starter shaft is worn.

After that, make sure fuel is flowing from the tank as I mentioned above. Then you can put in a clean/dry glow plug but do not hook up the igniter and crank it the same as testing flow. Then pull the glow plug, it should now be wet with fuel. If not, your carb is at issue. If it is, then try again with the igniter on. If compression is good it should start. Also when you are starting it, are you using the trim in your radio to open the throttle slightly? Most of these little motors need some extra air to get things moving.

 

[Freezectrl]

I have had issue with some exhaust seals on several engines. Some are too thin and do not seal properly. I had this issue until I found a good supplier when I was making and selling big block pipe adapters for the Revo 3.3 engines.

I researched a little on your starter and I think I am up to speed with you on it. If I saw it correctly then as you said there is no OWB. The starter shaft(15136) has 2 flats and the 2 set screws(Z721) lock the starter hex to the starter shaft. So it relies solely on the spring and pin for cranking the engine -correct?
So if you have slippage when cranking, either your set screws are loose/worn, the the spring/pin is sticking /not functioning or the end of the pin or edge of the lock groove in the starter shaft is worn.

After that, make sure fuel is flowing from the tank as I mentioned above. Then you can put in a clean/dry glow plug but do not hook up the igniter and crank it the same as testing flow. Then pull the glow plug, it should now be wet with fuel. If not, your carb is at issue. If it is, then try again with the igniter on. If compression is good it should start. Also when you are starting it, are you using the trim in your radio to open the throttle slightly? Most of these little motors need some extra air to get things moving.

Yes that's the one I had, the set screw was loose on the starter shaft. Also one of the set screws on the starter hex is cracked, it won't tighten down or come out (I'm guessing its expanding into the crack as I turn the screw driver and not catching)
I retighten the other set screw and it seems to grab, but that's probably why it slipped in the first place, only 1 set screw is holding it in place
I definitely will try the fuel flow test you suggested, I opened up the throttle before but didn't the last time

My oring just came today so I will be able to reinstall and try again tomorrow

 

[Freezectrl]

Welp, after 3 weeks of troubleshooting and fixing, I finally got my savage 4.6 to run today!
For one tank lmao
Turns out one screw trying to grab the starting shaft is not enough It slipped immediately as soon as there was oil on it
I got it to start once
So it's awesome that it starts, just now I have to somehow fix the set screw on the hex
Might have to buy a whole new nitro start backplate or rotostart, cause I don't think they sell that hex thing seperately..

Plus HPI being barely alive on life support doesn't help lol

Thanks everyone for the help! I can't believe I got it to run after all that, definitively needed every tip that was given here

 

[Rolex]

Good to hear it. Keep us posted, that's what we're here for.

 

[D3MON]

https://www.thobbies.com/products/hpi-109535
did find this, Thobbies is great to deal with, make sure though you are using their .com site, not the .net, the .net is their old one and doesn't put orders through, or show correct stock.