Tower of power detonation/ broken rings advice needed

[Jhoppy]

So here it goes the long story? two weeks ago I decided to go for a leisurely boat ride on the boat with my tower of power 1971 1350 serial number 3037534. Got her up and running let it warm up and proceeded to burn some of the cobwebs out across the lake it will run an easy 5800 rpm+ on my boat but I try to keep it below 5400. After a few short minuets of that I decided it would be fun just to put around the lake and look at some of the houses surrounding it and just enjoy the scenery. So keeping it at a slow pace about 2000 rpm or so I was circling the lake when the motor started to run and sound not so good. Thinking that it had probably loaded up on fuel I opened It back up across the lake now the max rpm was 5000 and the engine felt like it was missing. So I headed back to the ramp to do a little diagnostics and pulling one plug wire off at a time found # 3 hole was missing. Later that day I ran a compression test and #3 hole now had no compression and signs of detonation in the number 3 hole. Knowing at this point the engine had to come apart to make further diagnostics I pulled and split the power head finding #3 piston rings broke and missing and the # 5 piston rings broke and missing. The #3 hole has some light scoring and the rest of the cylinders are fine. So I plan on replacing the # 3 and #5 pistons and rings, honing out all 6 cylinders and putting it back together with maybe some new reeds? I?m looking at some Boyesen power reeds 65312b65 to replace the originals with.

The questions is why did this detonate. I bought this motor not that long ago and went though it and did some preventative maintenance replacing the upper and lower crank seals, timing belt wires plugs and floats needles and seats, I did not completely disassemble the carbs but did look at the main jet witch is .080 and appeared to be clean like the float bowl so I did not go farther with the carbs. I also did a link and sync like found in this form with max timing set to 21 degrees. I was running 89 octane 10% ethanol fuel mixed 50:1. This motor also has a new water pump impeller and pee?s fine and did not feel hot.

What did I do wrong, how do I fix it so it dose not happen again. I?m thinking maybe I need to back the timing off more and maybe run an octane booster in the fuel? Ethanol free premium fuel is hard to get now a days to is it better to run 87 octane without the ethanol or run the higher octane to beat the detonation and run the ethanol.

Also a pon disassembly of the motor I found out that the #3 and #5 pistons had been replaced once before because they were of the 2 ring design and had the power port hole and the other six are the three ring design and have now power port hole? Not sure If the different pistons are to blame but they all appear to be of the high dome verity because the dome was taller then .650 and measured about .750 not sure if the replacement pistons had something with it failing on those cylinders or if its something else?

Also how loose should the reed blocks fit around the crank shaft it seems to me that they should fit a little tighter than they appear to but I?m no expert so what is normal?

I?m sorry for rambling its past my bed time.

Thank you for any help and input/advice

 

[Chris1956]

Re: Tower of power detonation/ broken rings advice needed

It sounds like you covered all the bases. I do not have a suggestion, you have not considered.

If your reeds are intact, I doubt new reeds will improve things. Mixing and matching pistons is fine. Make sure you order the correct replacement pistons and rings for the entire motor. The 2 ringers are likely oversize. They use special keystone-shaped rings. The 3 ring pistons use rectangular rings.

Doublecheck the placement of the timing pointer to make sure the max spark advance is no more than 21* BTDC. If unsure, maybe back it down to 19*.

It is unusual for #5 piston/cylinder to break. Number 3 is normally damaged first, followed by #1.

 

[Faztbullet]

Re: Tower of power detonation/ broken rings advice needed

Make sure you prop it right as max rpm is 5400 (4800-5400rpm) at 5800 they will come apart.

 

[Jhoppy]

Re: Tower of power detonation/ broken rings advice needed

Thanks I will be sure to check the timing indicator and the piston rings to be sure they are right, and as far as the reeds there are a few that do not close completely when at rest what is acceptable here? I?m trying to avoid pulling this motor back apart in the near future.

I am a little hesitant to re prop though I like the lower end power when I comes to pulling skiers and tubers. Top end to me is not as important so I have just been throttling back to keep the rpm?s down. Is this an acceptable practice or is there a better alternative?

Any one have a recommendation for fuel grade minimum on these motors all that is available around here is 87 ethanol free and 89 and 91(I think still) with ethanol. Should I be running the 87 ethanol free with some octane booster to get the octane up?

Thanks

 

[Jhoppy]

Re: Tower of power detonation/ broken rings advice needed

Here are some pics the first one is the top of piston #5 and the last two are the sides of piston # 3
thanks

 

[daveswaves]

Re: Tower of power detonation/ broken rings advice needed

Some random thoughts here, what carbs are you using, do they have the the side tube and the vents in the bowl? .080 mains seem fat so it should not be running lean. At 2000 rpm it is just coming off the low speed circuit on to the high speed and obviously by the pics you were leaning out. I run 20 degrees and reg gas on mine with no problems.

 

[mr 88]

Re: Tower of power detonation/ broken rings advice needed

Sometimes old parts just fail,no matter what you do as preventive maintaince. My 1966 1100 SS I run at 40/45:1 and mix 1 gallon of 112 Octane to 4 gallons of 93.Gets the octane up, runs cleaner and I can leave timing at 21.Max suggested RPM is 48-5200 and I have it set up for 5200. If you need to find some 112 racing gas ask some local race car guys as that is what most use on the circle tracks. I also throw some seafoam in and put that anti ethanol blue stuff in on ocasion.Daveswaves is very knowledgable and spot on with info.

 

[CharlieB]

Re: Tower of power detonation/ broken rings advice needed

Looking at the pictures I don't see melting, I see collision marks from shrapenel passing thru the cyl, parts of broken rings.

The sides of the pistons smearing look more like an overheat which can break rings and pieces get above the piston making the indentations.

After cleaning the cyl and a very light hone your need to mic the cyls carefully to be sure of their finished size.

Piston clearance is critical to long life as too much clearance reduces heat transfer from the piston to the cyl and leads to this type of damage.

It may be best to mic ALL pistons and cyls, make sure that all are well within tolerance. You may need to bore and replace some pistons with over-size to get back into tolerance.

 

[Chris1956]

Re: Tower of power detonation/ broken rings advice needed

Maybe it is a combination of several factors? Slightly lean mid and bottom carbs, slight overheating on #3, slightly underpropped?

 

[Faztbullet]

Re: Tower of power detonation/ broken rings advice needed

I?m thinking maybe I need to back the timing off more and maybe run an octane booster in the fuel

Octane boosters are a waste of money in my opionion for a 2 stroke. Be careful if you add a race fuel to regular fuel as it will raise the the points a couple which is good as it decreases the chance of preignition but some fuels have added oxygenators that will cause higher combustion temps and cause it to run lean. That the reason they run cleaner as they are actually leaner.

 

[Jhoppy]

Re: Tower of power detonation/ broken rings advice needed

On the carburetors I was mistaken I am running the .0785 main jet not the .080 in them witch shows as stock in these motors and my book says that is the correct size up to 4000 ft, I?m at 2800 ft. should i be bumping up to a bigger main jet? As far as the carburetors the top says its a wmk-4-1 on the front of the bowl and has 0150654 cast in the bottom of the boal. The bottom two carburetors both also have wmk-4 stamped on the front of the carburetors and have 1399-3682 cast in the bottom idk what you mean by side tubes and vents in the bowl? Pictures included

I have taken a preliminary measurement of the bores and have found that out of round is within specks (under .003-.004 according to my book) but found taper to be on the high side on cylinder #3 as its .003 wider at the top vertically and .003 wider at the bottom horizontally if that makes since. but all else looks good.

Anyone here have thoughts on fuel water separators? I?m looking at going back together with one and loosing the little screen type filters in the carburetors when I go back together

Thanks

 

[mr 88]

Re: Tower of power detonation/ broken rings advice needed

Octane boosters are a waste of money in my opionion for a 2 stroke. Be careful if you add a race fuel to regular fuel as it will raise the the points a couple which is good as it decreases the chance of preignition but some fuels have added oxygenators that will cause higher combustion temps and cause it to run lean. That the reason they run cleaner as they are actually leaner.

This is true and I should have mentioned it.The four stroke racing gas is the type that is highly oxygenated and two is normaly not.You can smell the differnce, the 4 stroke will burn your eyes.I bump my burn time to about 97 octane and mix it because of the additives in pump gas and it keep me from re jetting in this case as I am at 450 above sea level.Not sure if it helps running it a little rich but i prefer to go that route.

 

[CharlieB]

Re: Tower of power detonation/ broken rings advice needed

Your jetting should be safe for your altitude, as long as the piston domes are in the black range you're fine.

Water seperator is always a good idea as is loosing the carb inlet screens.

Two strokes generally wear a 'belly' at the ports as there is less cyl wall to take the side loads. Measure carefully here just above and below the ports.

 

[Jhoppy]

Re: Tower of power detonation/ broken rings advice needed

Its been a long time since I tore this motor down and started this thread but finally its back out on the water and running good so now I can report back with most problems fixed I think?

I have to admit I am guilty and tried to cheat a little on this motor and got my hands slapped, the water baffle plate and water jacket cover gaskets are hard to find so I did not remove them the first time I had this motor apart

I had torn it down honed all six cylinders replaced the pistons and rings on cylinders 3 and 5 only and reassembled it using bands made from sheet metal to install the crank and six pistons at the same time, the bands I made to compress the rings did not work very well and my fingers bleed for days and later I found out I broke one ring that I could not see from the transfer port side,

I had not figured out why I was replacing pistons 3 and 5 again for the second time in this motors life, the only non original pistons and was suspicious of a repeat failure.

Got it running on the muffs and it seemed to run good but upon some careful inspection I found water on the spark plugs for cylinders 3 and 5 and all others were dry and that would explain why I lost these two cylinders and why they had went before, water was washing the cylinder walls down

so I removed all six spark plugs and the water jacket plug in the cylinder head cover and screwed a pipe nipple into the cylinder head water jacket cover and an old washing machine hose on the pipe nipple I hooked the block to the garden hose so that I could pressurize the cooling system without it running and adjusted water flow until pee hole flow looked about right using a boriscope I looked inside the cylinders it was hard to tell for sure but I could see water though the exhaust ports. And now I am thinking I wish I had removed the baffle plate when I had it apart.

So I pull the power head off the driveshaft housing again and used an old license plate and the exhaust adapter to build a make shift water block off plate for the cooling water inlet and outlet and used my pipe nipple and washing machine hose to pressurize the cooling system again and my suspicions were confirmed I was getting water into the exhaust jacket area as it was draining out were the exhaust should come out.

So I pull the baffle plate off and find that the inner water jacket cover is cracked just into the #3 hole allowing water into the cylinders 3 and 5 and that I had broke the lower #2 ring on the exhaust side I guess that?s what I get for trying to cut corners.

So I remove the crank, water jacket covers, and transfer port covers, order new rings and gaskets and take the inner water jacket cover and baffle plate to a local welder to have them repaired as I could not find new ones

and things did not go well from there the local welder ruined the baffle plate and inner water jacket cover and it took several attempts to buy the required baffle plate gasket but finally I found the right gaskets and the correct baffle plate and inner water jacket cover came up for sale on eBay so now I had what I needed to reassemble.

I had a much better Idea this time around on installing the pistons and crank as an assembly, I used a engine hoist and a strap to sling the crank and piston assembly above the block and lower it slowly with control and used an aluminum strap cut up into pieces 1/8 thick ? wide and 2 ? long with the edges and corners rounded. Using two peace of aluminum strap per piston I zip tied the straps to the pistons to hold the rings in place in the same way the mercury piston ring compresser compresses the rings, the strap fit down into the notches in the block the same way the mercury piston ring comprsser dose and once the piston was in far enough I cut the plastic zip ties and removed the peice of aluminum strap. I took some mock up pictures to explain. it worked very well and i did not brake any rings

The motor runs good now with compression ranging form 130 to 145 seems to have good power but rpm is down a little as it will only spin up to about 5200 rpm I am thinking that this may improve some after it has run a wile and brakes in.

I am loosing fuel pressure at certain conditions as I have explained in my other thread

http://forums.iboats.com/showthread.php?t=561264

I also started a thread on the inner water jacket cover/baffle plate
http://forums.iboats.com/showthread.php?t=551221


Thank you

Hoppy