1/5 rc 2 bolt vs 4 bolt for two stroke engine

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OctanE1

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I tried searching the web and here on the forums but cant find anything that answers my question.


what brings this question up is a F/S thread on another forum where a possible purchaser backed out of the sale, he thought the engine was a 4 bolt, because the seller had purchased an expensive exhaust pipe for the motor, the vehicle being sold is a losi 5t


Quote from thread:


No they came stock with the 26cc 2 bolt Zenoahs. I just assumed since you put a $200+ pipe on it that you put in a 4 bolt motor. Not many people would spend that kind of money on a pipe for a 2 bolt motor.


So what are the advantages and disadvantages of both?


What can you do with a 2 bolt head, or cant do?


What can you do with a 4 bolt head or cant do?


I just thought a 4 bolt gives you a better seal, and less chance of a bolt backing out causing an air leak.


Also I tried to make the title of this thread so that when you do a search chevy dodge and ford does not dominate the search, if their is a better title I could use let me know and I will edit it


Cheers OctanE
 
What u said.better sealing.i had nothing but problems with my 2 bolt.i always had head bolts snap and blew head gaskets.the 4 bolt is the only way to go imo....
 
The 4 bolt is less prone to blowing head gaskets and warping. They both make the same power and benefit from the same pipes. The extra 2 bolts give more sealing strength between the case and head.
 
What a moron. The 2 bolt has been used for many years and is still popular. Yes the 4 bolts is easier, but that doesn;t mean every 2 bolt should be thrown away.
 
one thing that helps on any of these hobby engines. when the bottom end cases are ready to be torqued down, the bolts that are towards the top of the cases will tend to squish the bottom end gasket more than the bolts towards the bottom of the cases. this is because of the top being open ends. a straight edge laid on top of the cases will have a gap if its torqued down to much. this is where quite a few leaks will occur. if a person assembles the bottom end with sealant instead of a gasket, none of this applies. permatex moto seal, yamabond, honda bond-ect. silicone is useless for this applacation.
 
here is a 2 bolt that has not has a easy life. been ran lean, ran with all the air intakes plugged with leaves-grass-mud- this engine has had about 4 gallons ran tru it. no leaks on this 2 bolt. not even a wet spot. its still up on compression, not a thing wrong with it.
 
Honestly, if you have a stock motor, a two bolt will be just fine.. Look at chainsaws and weed eaters, they run trouble free for years and I have yet to see one with head gasket issues.

When you increase compression and port a motor, this not only adds more HP but also a lot more strain on the internals, this is when you should think about a 4 bolt block for trouble free machine.
 
MrMeatHooks said:
Honestly, if you have a stock motor, a two bolt will be just fine.. Look at chainsaws and weed eaters, they run trouble free for years and I have yet to see one with head gasket issues. When you increase compression and port a motor, this not only adds more HP but also a lot more strain on the internals, this is when you should think about a 4 bolt block for trouble free machine.
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Yeah but were not jumping chainsaws and weed eaters 5-10 feet into the air, and landing at all angles:p ......but I get what you are saying.

Thanks for the replies hopefully the next person doing a web /goggle search will have this thread pull up to answer the question.
 
RampageHopUps said:
What a moron. The 2 bolt has been used for many years and is still popular. Yes the 4 bolts is easier, but that doesn;t mean every 2 bolt should be thrown away.
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This is a quote from the seller of the losi 5t he just posted this today on his F/S thread

QUOTE:

Well, shame on me then. Took it out today and pretty sure I blew the 2 bolt. Time for an OBR!!
 
Two bolts are fine if you torque the bolts like they are supposed to be and to keep from blowing gaskets use the copper ones with a little Motoseal and a drop of red Loctite on the bolts you'll never have an issue.
 
RampageHopUps said:
What a moron. The 2 bolt has been used for many years and is still popular. Yes the 4 bolts is easier, but that doesn;t mean every 2 bolt should be thrown away.
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So ur sayin i'm a moron for giving my opinion on motors.from the first time i ran my mt i had nothing but issues so for about the same price why would u buy a 2 bolt...fyi i been building diesel and gas motors for 25+ years so i'm more than qualified to know 4 bolt heads are better for sealing head to crank case better then 2 bolt heads.....

Use what u like and want but name calling is not needed....
 
Yep, and when they come out with an 8 bolt motor, that will seal better. Still don;t need to throw away your 2 bolts since something new came along.

I wasn;t calling you a moron in that initial thread. 25+ years is alot of experience in full size motors though. Hopefully you don;t tell your customers to buy a new modern engine every time a gasket blows.
 
Haha so i cant have an adult debate with out comment like a 8 bolt or new motor.i was just giving my opinion on a question.u like 2 bolt motors great..but when people upgrade then most often choose.4 bolts. u keep on saying about.throwing out all the 2 bolts i never said that u did...
 
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I couldn't resist. LOL
 
So on a 2 bolt if the head lifts and you blow a gasket, does that mean the head is done or can you just replace gasket and re-tighten the bolts?
 
Most of the time when you blow a gasket, you lean seize the motor. Not always, but people chase the tune and then find out later it was an air leak.
 
OctanE said:
So on a 2 bolt if the head lifts and you blow a gasket, does that mean the head is done or can you just replace gasket and re-tighten the bolts?
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I had a head gasket blow on my two bolt. I pulled the head off port it and the piston went down to my local small engine shop and picked up a gasket. Bolted it all back and it fired up on the 3rd pull. Now it scream like a raped ape. There is no need to replace the whole engine just cause the gasket went bad.
 
I will give 4 bolt motors a shot if my RAMtech 36 ever dies. Right now, it runs great and have had ZERO issues with it. But again, compression and power output are the main issues to be worried about when talking 2 bolt vs 4 bolt comparisons. Another option is to make your own gaskets. I use automotive grade stuff that is tough, you wont blow it out. A little fuel proof sealer will help also. Good choices if you are worried about gaskets blowing, a lot better then throwing money out for a 4 bolt.
 
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