Fuel for OPS .21 3.5cc

[Terry Keeley]

You're watching too many YouTube videos and not taking the advice from folks here that have been doing this at a very high level for many, many years.

Go back and re-read post 57 Grasshopper, lol!

 

[Jim Zelazny jr]

Haha...somehow I misread your post.This makes the most sense actually.
Case of overthinking...just hate to put these in and have to take back out again I guess.
Going to do it now.

 

[Terry Keeley]

Do it like post 29, do it now!

 

[Jim Zelazny jr]

LOL...Warming the block now and will drop them in.Here goes

 

[Jim Zelazny jr]

Well that was easier than I expected...both dropped right in nice.20 minutes in the oven to remove and replace.

 

[Mark Stein]

The life of those bearings depends on lubrication. If you have have not installed them yet remove both shields on the big bearing and at least the shield that faces the inside on the small bearing. The only lubrication the small bearing is going to get must go thru the large bearing then thru a only slightly larger hole that crank goes thru the has to some how get to the small bearing. If you leave the inner shield on the lubrication has a harder time getting in. Also if you are running the normal cable setup all of the load of pushing the boat thru the water is transmitted directly to that small bearing. One more thing to consider. Rc car motors never see an end load unless it is a multi gear setup and then only for a split second as it shifts. Cars and trucks can coast a boat will never coast until you shut the engine off. Shock loads from launch and prop leaving the water all is transmitted directly to that small bearing. Best to remove all the shields.
Terry has definitely got you on the right trac. Check the outside diameter on the large end of the new rod and the old one and measure the center to center length of bottom and top holes. You may not have enough clearance inside the case to allow use of the new style rod. There are also long stroke short stroke and nuetral stroked .21 engines (under square., over square and square ) concerning the bore and stroke all have the same displacement but different way the engine produces power.

 

[Jim Zelazny jr]

Mark,than k you for added details and tips.Both shields were removed from the larger bearing and the inner shield removed on the smaller one.I left the outer bearing on facing the driveshaft.I may have removed them all as for obvious reasons,guys that run cars in dirt like to have the shields where in a boat,really not an issue.But I already did it that way.
The new con rod will be here this week.It claims to be old stock part but as you mentioned,I will need to be absolute about measurements.I understand what you are saying that if it is not proper,could be catastrophic considering the RPM`s this thing produces.I will check this carefully and post here with details as I do not want to destroy the engine.If I have to eat this rod and find another one,so be it.I try to use common sense about the bearing stuff...makes sense removing to covers that were inside the engine for obvious reasons...OIL.
Rebuild is on hold for now until the rod arrives,but going to finish work on the carb and get it cleaned up ready to mount up.I am grateful for the patience and tips here on the forum.I am fairly good at using tools and engine knowledge,but this nitro stuff although similar requires guidance for me.Working with the smaller components come easy for me as I design and build my own PCB electronic boards using SMD components.So lots of practice handling sensitive things.Dennis from GoNitro has sent out a gasket to me for the crankcase cover plate.Meanwhile,going to get the new bolts and work on carb.I think it will work out ok...we will see when rod gets here.
Jim

 

[Jim Zelazny jr]

I know we already talked about piston orientation as the wrist pin has a closed end and open end.
But think Terry mentioned closed end on exhaust side (post #33) ? Either way neither side of pin faces exhaust as the exhaust port is on the side of engine...maybe I misread and was the carb intake side that receives the closed end ? Just double checking this even though I am pretty sure I noted which way it came out.

 

[Geraghty]

I know we already talked about piston orientation as the wrist pin has a closed end and open end.
But think Terry mentioned closed end on exhaust side (post #33) ? Either way neither side of pin faces exhaust as the exhaust port is on the side of engine...maybe I misread and was the carb intake side that receives the closed end ? Just double checking this even though I am pretty sure I noted which way it came out.

RE: The wrist pin orientation on your side port ....On your motor this isn't even a consideration.....your wrist pin never sees the exhaust port....
One thing you should consider is if there is a chamfer on the lower rod bushing it should be facing the counter balance face when installed on the crank pin....You want the crank pin radius to match with the rod chamfer ...

 

[Jim Zelazny jr]

Here is an image when I removed the piston and rod and set it on the table as it was removed with cover off facing me.Basically the carb facing opposite direction.I have not removed the con rod from the piston yet until new arrives.But note the hole in the con rod bushing,so for sure I know which way the piston will go for assembly and will note the open/closed wrist pin location and return that way.I like photos as I go for reference in the event I forget what went where.

 

[Terry Keeley]

RE: The wrist pin orientation on your side port ....On your motor this isn't even a consideration.....your wrist pin never sees the exhaust port....
One thing you should consider is if there is a chamfer on the lower rod bushing it should be facing the counter balance face when installed on the crank pin....You want the crank pin radius to match with the rod chamfer ...

Rod's right, forgot it was a side port, haven't seen one in 30 years!

As mentioned if you don't see a champher on only one side of the rod look for a darker area on the piston, that will be the exhaust side.

May as well pull the rod, use some forceps or fine needle nose pliers to grab the little tang on the c-clip and gently pull it out with a twisting motion. Try not to loose it! The wrist pin should push right out from the opposite side.

 

[Jim Zelazny jr]

Believe it or not,this piston has no dark sides...not even the top.Thing is really clean as it was pulled out.I will investigate differences of everything on this rod/piston.I have looked it over pretty good under magnifying lens,other than the bushing hole and open/closed wrist pin differences...I see nothing else.
Heading to local hobby shop soon to see if they carry the bolts I need.Also to see what parts they may magically carry tucked away from days past.

 

[Terry Keeley]

Believe it or not,this piston has no dark sides...not even the top.Thing is really clean as it was pulled out.I will investigate differences of everything on this rod/piston.I have looked it over pretty good under magnifying lens,other than the bushing hole and open/closed wrist pin differences...I see nothing else.
Heading to local hobby shop soon to see if they carry the bolts I need.Also to see what parts they may magically carry tucked away from days past.

You might see more scuffing on the exhaust side also. If there's only one bushing hole in the rod it was probably aligned to force fuel into it while running. The motor turns clockwise looking from the back.

Ask the hobby shop if they have any head gaskets that will fit. They'll be copper, brass or aluminum.

 

[Jim Zelazny jr]

Yes...going to see what they have in every way shape or form.Also interested in who their contacts are.Maybe they have stock on these engines somewhere...not holding my breath. I was going to visit the other hobby shop that is actually not far from the first...but closed on Sunday? Seems odd as that would be the money day in my opinion.

 

[Jim Zelazny jr]

Hobby shop on Sunday was run by people who did not want to be there.Managed to get the bolts I needed and made attempt about gaskets...but the people there seemed uninterested,unenthusiastic and really did not know a **** thing about what I wanted.All I wanted was the guy to LOOK for gaskets that MAY work.I mean really...I am sure of all the engines out there,one would be similar? At least TRY ? Frustrating when you drive 20 miles and want to get all you need possible in ONE trip.So I walked out with 4 bolts and a glow plug.Oh...and an expensive throw away file that looked like a file for finger nails...geesh.Stopped at hardware store (Home Depot) and grabbed RTV sealant and the JB weld for that carb repair.The 2 part JB weld worked great.I already applied,let dry over night and filed it smooth.The carb slips into the port nicely again.I will use a tiny amount of RTV gasket sealant in the end...TINY amount.Now ,waiting on gasket and con rod in mail box...then put this back together.

 

[Jim Zelazny jr]

Ok...new rod just came in and wasted no time to compare both.
I know for sure already the new will not fit into the piston,it is just a mm too wide if that.
Here are differences in general the best way I can without precise tools.
Can it be made to work or am I back to square one here?
Jim

 

[Jim Zelazny jr]

For fun,put the rod in the block and slid onto crank pin.The crank turns without anything touching,but it IS a bit closer to the case which sounds like a bad idea even if I was to grind the width from the wrist pin end so it would fit.Wish the wrist pin end was the only difference in these rods but the crank end is beefier on this new rod.I would take and have it milled down but not sure if it is easier to just find the right one?
Going to add another note about the new rod...it has 2 oil holes on one side.

 

[Terry Keeley]

If it fits the case and you just need to thin out the top end go for it.

You won't hurt anything and it'll be better that an old stock rod that has no upper bushing.

Know anyone with a mill?

 

[Jim Zelazny jr]

After 300 emails and searching the entire day here,I am gonna just take my file and run it over both sides of the piston end on the new rod.Only need to take off .5mm on each side anyhow so it will fit between the piston pin openings.The crank end of the rod has more material and is closer to the crank case,but not touching.I wonder if I can shave a tad of each side of that too as I do not know about metal expanding and RPM combination will cause issue.This engine and finding parts is no fun...so gonna use my skills here.

 

[Jim Zelazny jr]

Gonna ask my nephew now about taking to machine shop.