half tank lean

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Thanks JR, that makes it a bit clearer, i wasn't doubting it worked, just trying to understand how. Must be a pain to fill the header tank before a days bashing though. i see yours has a lid so you can fill it, but the ones i've seen seem to be sealed, its gonna talke a fair few gentle pulls on my starter to fill it! :confused:
 
what i do is i use a primer ball filter then run from the main tank to the top port on the header ,then i run the lower port on the header to the carb. what you have to do on the first tank is remove the line off the carb and hold it in the air above the truck.fill the main tank as normal. then use the primer ball to fill the header tank. if you don't hold the carb line in the air it will flood the engine and never fill the header tank.i usally can prime the header tank almost full. then i reconnect the carb line and start the engine as normal.usally by the time i get the body on the header tank is completly full. i usally run the truck til the main tank is empty that way i don't have to refill the header tank. i usally remove the carb line and plug the exhaust pipe to turn it off.if you don't remove the carb line on shutoff then it will flood the engine badly for the next start up.on the last run of the day i let the engine use all the fuel inside the header tank so it dosent sit with it full til i run the truck again. it sounds like a pain but it really isnt and its worth it because it really dose work to eliminate the half tank lean problem. it also makes the engine run a lot better and stays more consistent most of the time. i hardly have to mess with the carb settings. i hope this helps.. john...
 
Know what's weird... I don't know what yall are talking about... I've never had the problem.... wonder why not.. I've used 2 gallons
 
they put a header tank on there and it keeps it from leaning out when you have about half a tank of fuel left hence 'half tank lean'
 
some people get it and others say they never have had it. i don't understand why, the only thing i can figgure is maby if you are tuning for optominal preformance or staying on the rich side. my orginal 4.6 engine didnt start doing it til i got to the almost 2 gallon mark. it was bad and did it noomatter how rich i set the carb. it was so bad that the engine barely ran til i got just at 1/2 tank, then it ran good but it was a real pain having to tune the carb all the time.oh well if you have it do the header tank mod and it will fix it .
 
HPI_Savage25 said:
Know what's weird... I don't know what yall are talking about... I've never had the problem.... wonder why not.. I've used 2 gallons

What kind of temp gun are you using, and where on the motor are you checking the temp? The reason I ask is because the 1/2 tank lean is a design flaw, and it should effect every savage.
 
Well i go to my lhs since he knows me and my dad reallllllllly good. so he lets me drive it their and testes it... he testr on the head
 
does the mid tank mod help this out?...because you actually putt the whole tank above the carb inlet.When my motor starts leaning it's self out i know it's time to come on in for fuel and a little cool down.....so it didn't really pose to much of a problem for me yet.
 
from what iv tried. i didnt like a mid tank because it cut down on the ammount of fuel i could run.and putting tha entire tank above the carb made my truck get flooded very easialy. and hard to start. the header tank mod is cheap and easy and dosent change the electronics box to make it work.i think i have 3 dollars into my header tank and maby 8 in a filter/primer ball , and i didnt have to mod anything to make it work. i just attached it to the rear shock tower with a zip tye. its really easy to do and fixes all running problems due to the bad tank design.
 
If the mid-tank is done right the tank is no higher than the stock tank. The design flaw is in the stock tank itself. Brcause the tank changes shape halfway down, the pressure changes when it gets to that "ledge" on the inside of the tank. At that point there is alot more volume to fill before applying pressure to the fuel. Adding a mid tank has nothing to do with the height of the tank itself, but the reason it works is it gets rid of the troublesome stock tank alltogether and replaces it with a properly designed tank. My next mid tank will be using a MGT tank so I don't lose as much run time.

HPI_Savage25 said:
Well i go to my lhs since he knows me and my dad reallllllllly good. so he lets me drive it their and testes it... he testr on the head

I strongly suggest getting a cheap lazer temp gauge like a duratrax flashpoint, and checking it periodicly throughout the tank. If you are running a savage with a stock tank, you have the 1/2 tank lean. You wont know by the way it's running, only by the temps. And when you check your temp, make sure you are checking it at the glow plug, and not the cooling head.
 
My half tank lean problem is so bad that it almost seems the engine can`t hold a tune.
I`ve gotta go to the lhs tuesday to order some tranny parts and I think I`ll get some larger diam. fuel line and put it between the exhaust & fuel cap and I`ll try to grind out the connector on the exhaust.
I already made the fuel lines a bit shorter and it seems to help but it`s still so bad that I don`t need a temp gauge to see that I got the half tank lean issue
 
yep mine was so bad i had to retune to get it to run with a full tank. it slowly got worse. when i first got my truck it was runing fine then i started noticing it as i was tuning for performance after breakin. i went through 2 hpi 4.6 engines so after i put in the first replacement engine, i went til breakin was over then it started again. then i went to a picco .27 after the second hpi engine came appart, then i didnt see the half tank til i got through the breakin with the picco.mine was so bad after i filled the tank to run again it was so boggy that i had to lean the hsn almost a full 2 turns in to be able to run it til it burned down to half tank.then all of a sudden the engine would start screaming and smoke trali would go away and the temps would rise. my temps would go almost 75 degrees within one lap.it was like someone would turn on a light switch. once i tuned it good for half tank it would run fine. i could fill it only half way and run from there and all would be good. i even would start at half tank but runtimes were cut in half, so id run it til it was almost empty and then refil to half tank without shutting it off . that got to be a pain too.then it started getting worse even at half tank. i don't know what starts it , iv got theorys about it, all don't make any sense ,neither dose the reason it seems to get worse. i even think maby my first 2 engines might of blown because of it.
 
Yeah, this is the reason I am very dissapointed with HPI right now. They came out with the savage X, they had an oppertunity to fix their biggest problem but they left that same old tank on there. The other changes were great, but as a brand new savage comes, it is set to self destruct. I have seen temps that topped 400* after running fine at 240* the first half of the tank. It is something that is fixable, but is one of the reasons I no longer have a savage. I loved the trucks, hated the tanks. I despise the fact I have to lessen my runtime to fix a problem that HPI wont recognise. OK, rant over, I will put my soapbox away :).
 
if the problem is with the design of the tank it self and not where it sits from what i have read. couldent you just swap tanks with some thing that does work.

also how big of a tank do you have to have for a header tank cause i have a old plane tank that looks like the one in the pics i think will work. and where do i get the primer/filter ball. cause i think that i may have exspeirence this with my ofna motor and wwonder if it wikk efect me with my o.s 30 max motor since it is a biger motor wont it take more fuel
 
Wow great thread I learned alot. I definately have the half tank lean prob and didnt know it.
 

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