Help wont crank

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bobbd

Well-Known Member
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Hey guys I got 2 new hpi savage 4.6 I took noth engines apart and sealed just went out today to break both in but rotostarts wont crank engines and rotostarts trip their fuse..I took spark plugs out of both and turned fly wheels and it looks like the pistons are not going up and down... help
 
I’m definitely no expert... but, it sounds like you might have put the one way bearing in backwards.
 
I agree check the owb like renots said. Especially if the piston isn’t going up and down with the glow plug out.
 
Ok but roto start wont turn it a hair it locks up then rotostart trips fuse. Rotostarts works fine when not engaged with engine. I thought if one way bearing is installed backwards it would just slip not lock up..
 
Are the engines new? If so you may want to crack the glow plug open a little when you try to crank and once it fires up tighten plug back up, you could be hydrolocking the engine because the compression is a little tight since the engine is new.
 
Yep they are new but I took spark plugs out and tried to turn over wont budge with roto start either engine
 
Does anyone know if u put the one way bearing in backwards in a savage 4.6 would it lock up or just free spin when trying to start with a roto start?
 
sounds like you put the piston and rod in backwards, some pics would help alot in diagnosing your issue....
 
If I turn one way bearing to the right (clockwise) it just spins free no piston movement if I turn it left (counter clockwise) every full turn20190519_132005.jpg it makes a clicking sound and also no piston movement.
 
Ok thats cool, did you try cleaning the 1 way in some motor spray or denatured alcohol, I clean mine with DNA and use a toothpick tool to put some red grease down into the rollers inside, i go all the way around the inside of the bearing , it helps it to not absorb the oil from the engine which is the main culprit of it slipping......
 
When I turn the one way bearing with my hand to right it spins freely but piston doesn't budge if I turn it to the left with my hand it turns and makes a clicking sound with no piston movement but when I put rotostart back plate on and try to start engine with rotostart it wont budge not a hair. What gives ?
 
So with the glow pugs completely out it still will not spin at all? How are you priming the engines?
 
Griff yes the glow plugs out it will not turn over wont budge piston wont move on both new engines. I'm not priming cause piston wont budge
 
you are going to need to do some disassembly to find the problem, one thing, can you rotate the flywheel and make the piston move through a stroke?? if so I think you either lost the pin and spring in the end of the crank pin or did not install it correctly... some clear pics inside the backplate will help alot
 
https://www.hpiracing.com/assets/documents/instruction_manuals/i1495-f46-glb-m-v1.pdf

Check the engine rebuilding section in the linked manual, note part # 1433 and how it goes into the end of the crankpin, if that is not in place your engine will not crank and may get jammed by the pin and spring being out of place.......

You can also see a better pic in section 7 of that manual..... put the spring in first and the pin after, it helps to put a small dab of grease in the hole before setting the spring and pin in place.....
 
Thanks Jam , yes the flywheel makes the piston ride up and down but the 1 way bearing installed the way the manual shows (see picture) will just spin freely clockwise and counter clock wise and no piston movement ......I pulled 1 way bearing off and installed it the opposite way (see 2nd picture) with flat side towards engine block and WALA it now makes piston crank when turned clockwise..could it be the directions i20190520_165025.jpg20190520_165129.jpgn the manual that came with the savage are wrong...?
 
well it does show the bearing shoulder part in toward the block so maybe you did have it wrong, remember to pay better attention when you are taking things apart next time, take pics like i do so I don't have one of those brain fart moments... :lmao:
 
Jam I had the shoulder in towards the block the way the manual shows but it does not work that way I turned the 1 way bearing around so shoulder is facing the rotostart plate the exact opposite of the way in manual and it works...no brain fart...whoever made the manual had the brainfart I guess . But does anyone know if that's the correct way -1 way bearing shoulder facing away from back plate like this pic of my engine..20190520_185450.jpg
 
I believe the arrow you see on the inside race of the OWB is the direction the shaft should spin. So it appears that you need to have the bearing with it backwards from the diagram. It's like you got bearings that had the outer sleeve installed wrong.

If you look at the photo of the OWB on amain, you can see that has the end with the arrow/text on it not flush with the hex.
https://www.amainhobbies.com/hpi-pullstart-one-way-bearing-21bb-s25-f4.1-hpi1430/p25545

Same on dollar hobbies:
https://www.dollarhobbyz.com/collec...-g3-0-backplate-one-way-bearing-starter-shaft

But if you look at others on dollar hobbies, you see it's like yours, the end with the markings/arrow is flush with the outside:
https://www.dollarhobbyz.com/collec...-4-6-nitro-star-f4-6-14mm-hex-one-way-bearing

And it's the same on HPI's site, backwards:
http://www.hpiracing.com/en/part/107829

It should work fine, it just won't be keyed into the starter gear's hex as far and it might slightly rub the backplate a bit more.

The clicking your hearing is kind of a weird design with those engines. The shaft that goes through the OWB has a flat disk inside the engine with a channel that goes from flush to 2mm or so deep. The pin that is in the crankshaft that catches on the end of the channel wall has a spring pushing it out and applying constant pressure to the plate. Once the engine starts, the pin slides on the disk and doesn't catch because the channel goes from flush to not flush. Not sure if it's a safety thing or assembly assist or what, but they are the only engines I've seen built that way.

You can see it here:
firestorm_backplate_3f7fb605-7916-4356-8800-73a8e9df56cd_1024x1024.jpg
 
Thanks Olds for your time and answer as usual..I feel better about running it now.
 
You are right as usual Olds after further inspection of owb the arrow is on the flat side indicating arrow right if put on shaft with flat side of owb. Hpi screwed up on both my new trucks but at least it was an easy fix by installing the opposite of manual...sure glad I didnt have to take the back plate off which was already sealed ....thanks again to every one who chimed in. Great site.20190521_172955.jpg
 
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