Hpi Savage 21 rebuild and restore thread.

[Starfox2005]

This is the first nitro RC truck or (nitro) land vehicle that I've owned so any advice or suggestions are appreciated! Big thanks to @HZRDOS for the truck! I have gotten the engine loosened and unstuck! Here's what's happened so far.

 

[gotnitro]

Why did the engine need to be loosened or unstuck? Was that piston left at TDC?

 

[Starfox2005]

Why did the engine need to be loosened or unstuck? Was that piston left at TDC?

It was seized at TDC I got it fixed and it has a lot of compression in it.
All you had to do to fix it was fill the crankcase with fuel and use a heat gun to heat it up and it worked out the gunk. I also put after run oil on the piston to help it lubricate the cylinder above the piston. You definitely need to be careful with a heat source and fuel though!!

 

[gotnitro]

It was seized at TDC I got it fixed and it has a lot of compression in it.

Have you popped it yet? Sometimes when they heat up you will notice there is no pinch (compression) left in the sleeve, they start to lose the tune and run like crap. 2 options at that point. New matching piston and sleeve (I would do the wrist pin and rod if it were mine at that point or a brand-new mill depending on where you are at pricing) OR having someone pinch the sleeve and run good fuel like VP-20.

 

[KnowAir]

Congrats on the new rig!! Savage is a legend for sure.
Just out of curiosity, are parts still available for these? The motor is an easy fix/replace, parts would be the deciding factor for me.

 

[HZRDOS]

Sweet. I had a lot of fun with that thing 20 years ago! Was my first fast RC beyond Tamiya buggies. Can't wait to see it run!

 

[Starfox2005]

I've gotten the engine to run and it will need re-tuned and there's a air leak from the carb seal on the block so I'll need to seal that up.
Header before polishing-

After polishing with a Dremel tool.

Have you popped it yet? Sometimes when they heat up you will notice there is no pinch (compression) left in the sleeve, they start to lose the tune and run like crap. 2 options at that point. New matching piston and sleeve (I would do the wrist pin and rod if it were mine at that point or a brand-new mill depending on where you are at pricing) OR having someone pinch the sleeve and run good fuel like VP-20.

Yeah it's run up to temp. It seems to run a little funny though I think it's because of a air leak by the carb so when the carb get closed it will feed off that air leak. I'll take the carb off and seal that when I get a chance this weekend. It probably needs a new tune on it also.

 

[gotnitro]

I've gotten the engine to run and it will need re-tuned and there's a air leak from the carb seal on the block so I'll need to seal that up.
Header before polishing-View attachment 243339
After polishing with a Dremel tool.View attachment 243340

Yeah it's run up to temp. It seems to run a little funny though I think it's because of a air leak by the carb so when the carb get closed it will feed off that air leak. I'll take the carb off and seal that when I get a chance this weekend. It probably needs a new tune on it also.

Usually, you'll get an air leak through the front bearing, very common in RTR or RTR replacement engines. Good luck, I never had patients for air leaks, they would become projectiles at the nearest garbage can.

 

[KnowAir]

Usually, you'll get an air leak through the front bearing, very common in RTR or RTR replacement engines. Good luck, I never had patients for air leaks, they would become projectiles at the nearest garbage can.

I always bought cheap niteo motors back in the day for that very reason..run em till they start acting up, then toss and start over.
The best motor I ever used was an OS. 15 CV I believe? 1/10 stadium truck. OS was made in Japan at that time, not sure if that's still the case. Went through quite a few others, TRX, Thunder Tiger. TRX had the exchange program, but that got old..they didn't really last for me. The OS however outlasted any other I tried. Tuning is such a critical part with nitros though.

 

[gotnitro]

I always bought cheap niteo motors back in the day for that very reason..run em till they start acting up, then toss and start over.
The best motor I ever used was an OS. 15 CV I believe? 1/10 stadium truck. OS was made in Japan at that time, not sure if that's still the case. Went through quite a few others, TRX, Thunder Tiger. TRX had the exchange program, but that got old..they didn't really last for me. The OS however outlasted any other I tried. Tuning is such a critical part with nitros though.

Any RTR nitro I've owned always got the OS replacement for those exact reasons. There is just no comparison in Japan tolerances or QC. I've never owned an OS that had an air leak or any problems other than general wear n tear. I got over 12 gallons through almost all my OS RACE engines before I needed to pinch the sleeves. RTR mass produced crap, be lucky to get 4-6 gallons.

OP, when you tune the HSN, look at the needle like a clock, tune in 3 min increments, very small adjustments. Make sure it's a little on the fat side, once that tank starts to get below 1/2, they start to lean out.

 

[Exc3l]

Also, check the gas tank cap. The o-ring can go bad and an air leak is super common. Carb seal is possible but I have not had an issue with that. Looks great. Enjoy

 

[slick2500]

Any RTR nitro I've owned always got the OS replacement for those exact reasons. There is just no comparison in Japan tolerances or QC. I've never owned an OS that had an air leak or any problems other than general wear n tear. I got over 12 gallons through almost all my OS RACE engines before I needed to pinch the sleeves. RTR mass produced crap, be lucky to get 4-6 gallons.

OP, when you tune the HSN, look at the needle like a clock, tune in 3 min increments, very small adjustments. Make sure it's a little on the fat side, once that tank starts to get below 1/2, they start to lean out.

I know this is going to sound like a few stupid questions but I see this problem with a lot of nitro monster trucks what causes it and why don't they fix it?

 

[Rowdyray]

Any RTR nitro I've owned always got the OS replacement for those exact reasons. There is just no comparison in Japan tolerances or QC. I've never owned an OS that had an air leak or any problems other than general wear n tear. I got over 12 gallons through almost all my OS RACE engines before I needed to pinch the sleeves. RTR mass produced crap, be lucky to get 4-6 gallons.

OP, when you tune the HSN, look at the needle like a clock, tune in 3 min increments, very small adjustments. Make sure it's a little on the fat side, once that tank starts to get below 1/2, they start to lean out.

We did the same thing. Usually ran the RTR until it died. Replaced it with an OS. Never had an issue with any of them. A lot of that had to do with fuel, tuning and maintenance. I know others claimed their engines had more HP or RPMs. Blah...blah....blah. None lasted as long as the OS. My oldest son still has his first RC. Nitro Rustler. Replaced the RTR 20 yrs ago with an OS .15 and the Stinger pipe. Uses after run oil when putting it away for the winter and spins it over a few times while stored. Had it out a couple weeks ago. Still stupid fun. We were trying to figure it out. At least 10 gallons through it.

 

[Rowdyray]

@Starfox2005, is that the Axial .28? If you can get it running right, great. But, don't waste too much time on it. Not the greatest engines. My brother got a great deal on the same RC. Toasted RTR .21. Bought an Axial .21. Never got it to run right. Returned it and it was worse than the first. It's still sitting in a box in his basement. Bummer, because they're a blast. Really hoped he could rip with me. I have the SS 4.6 version. Too many upgrades to list. Original engine. Had it out last summer. Still a beast. Too focused on the new Arrma rigs for me and the kids this year.

Love seeing others restore them and wish you the best. Makes me want to drag a couple out from the dead.

 

[gotnitro]

I know this is going to sound like a few stupid questions but I see this problem with a lot of nitro monster trucks what causes it and why don't they fix it?

Well…

China made
No matching pistons and sleeves
Piston skirts are thinner than a Trojan
Rods and blocks are milled from pop can aluminum AND mass poured
Bearings are cheap and mass purchased with no real QC
Carbs are

I used to wear split crapsucks rods on a broken mill necklace

I don’t think they will fix it because they know most will go out looking for more power in a larger mill and those that don’t will most likely never break because they are content leaving it alone on the shelf. Yeah, that’s da ticket..

 

[slick2500]

Well…

China made
No matching pistons and sleeves
Piston skirts are thinner than a Trojan
Rods and blocks are milled from pop can aluminum AND mass poured
Bearings are cheap and mass purchased with no real QC
Carbs are

I used to wear split crapsucks rods on a broken mill necklace

I don’t think they will fix it because they know most will go out looking for more power in a larger mill and those that don’t will most likely never break because they are content leaving it alone on the shelf. Yeah, that’s da ticket..

Shoot my bad I should have been more specific. I wasn't talking about the motors dying I was asking about the 1/2 tank lean out.

 

[gotnitro]

Shoot my bad I should have been more specific. I wasn't talking about the motors dying I was asking about the 1/2 tank lean out.

The less fuel in the tank the less pressure you have pushing fuel to the carb. At about 1/2 the carb starts to pull and lean out.

You will see race guys stabbing the throttle over and over when pitting while their pit guy is shooting fuel into the tank as fast as he can, they are trying to avoid stalling. Not from cold fuel but from it getting very FAT very quickly. Usually happens when they snap the tank lid shut, it forces fuel into the carb and boom, stalled.. AKA in the race world, a flame out.

 

[HZRDOS]

Alright man - so where are the running vids of this thing?

 

[Starfox2005]

Alright man - so where are the running vids of this thing?

Haven't gotten to that point in the build yet. It needs tuned up but I do have some video of the first startup and bench run.
Needs brake work because right now it has no brakes... I think the cam shaft lip is bad because it keeps sliding out. Haven't had a lot of time recently to work on it. I was really hoping to tune it over this weekend but forgot about my marching band schedule. It's even more intensive because I'm in the drumline and we practice even more during the week.

 

[Starfox2005]

I tried to start it and it wouldn't fire and felt like it had no compression so I took the head off to find this. I can just replace the shim and it should be alright right? 2nd pic is before.