Seized Engines Honda Elite Big Bore

[dem0nk1d]

Keep nuking engines, why? What would cause two 'Big Bore' jug kits to fail in the same way?

First run with the 70cc 'Big Bore Jug Kit' was pretty much all stock parts including the stock carb. After test driving the piston seized into the cylinder walls. My first thought that it was because of the stock carb.

Then i decided to order the same kit, but with a 28mm OKI CARB, jet kit, performance intake manifold and reed cage. Ok so my second run. Called up some scooter shops out in Hawaii to figure out which main and slow jet the run, because living in San Diego the climate is some what the same.

Second run new 70cc Big Bore. Everything ran excellent tons of power, kept throttle down to a 1/3 of the way. Then stopped let the engine cool down for an hour or so, and then back into the initial break in process. Once I thought the engine was fine, I decided to go on a short ride 10-15 miles or so. The first 3 miles the scooter just hauled with tons of power, then all of a sudden the bike just stopped. I quickly pulled off the super hot exhaust to check piston wear. What do you know? Another piston seized into the cylinder walls.

So I guess i'm asking what's wrong with this engine? Do you think it could have been a badly out of round Jug? Or do you think it's possible the crank bearings are shot and is causing the engine to overheat and seize?

Also if i have to look into buying a new engine case. Will the Fake gy6 50cc engines mount up and will i be able to use all the honda dio components?

My scooter is a 88 Honda Elite with a newer 98 Elite Engine in it that i bought used.

[Wheelman-111]

Greetings:

And welcome to the Forum. Sorry for your misfortune.

Two things occur to me as possible contributors to your seizures. I mean your scooter's...

Both bores need additional oil to be supplied. The stock pump is calibrated to match the fuel inhaled in 50cc gulps, matching the correct quantity of oil for that amount of fuel demand. When you increase displacement 40% or more, either the pump must supply more oil or you must add a little to the fuel as premix.

The consensus of most tuners is to eliminate the pump - it must be removed bacause it can't run dry for long. A blind plug or some sort of case stuffer is inserted in its place. Then pre-mix at your chosen ratio. Nobody here seems to have any specific opinion as to what that is, but Honda's 2-Stroke oil containers say 32:1 for motocross racing. Sounds like a reasonable place to start.

My objection to this regimen is that the oil comes in at 32:1 whether you're idling at a signal or racing down the boulevard wide open. Maybe 32:1 is too much for the former, not enough for the latter. That's why most pumps are cable-controlled, after all. Decreasing oil supply to the cool idling engine and increasing when there's lots of heat being produced makes sense to me. For that reason, I premix at 60:1 and adjust the pump to open all the way early. So far (5 bores in all) no engine damage. However if you switch to this program, be advised that an upjet may be necessary. See below.

The second thing is jetting. If the kit you bought didn't come with a replacement jet, it needed one. Polini's Contesta 65 for the Aero upped the stock 82 to an 85, and that was pretty conservative. 88 would be better, even with stock pipe. Whomever sold you that OKO carb should have a pretty good idea of the jets for your second setup, so see above.

Crankshaft bearings and crooked cranks can cause issues, but we don't need that to explain what happened to your scooter.

GY-6es are 4-strokes and nothing from your Elite will fit. We never speak of those engines here.

Good luck with bore #3 and welcome once again.

[dem0nk1d]

I guess I should have included that i have eliminated the stock oil pump, and went with a premix. I'm not sure what it was but that's not relevant at this time. I'm going to look into stroker crank and rod, with a big bore. Then go back to square one. I'm really excited there is a forum finally supporting the Elite's and Spree's.

Back to square one for me. =)

[wiguy05]

Most likely lean condition on the main jet. Contrary to what you believe, I highly doubt San Diego's climate is very similar to that of Hawaii's.

Lack of oil could also be a possibility and BRAND/TYPE of oil DOES matter.

[bradthreee]

What kind of kit are you running? Made in tiawan?

[dem0nk1d]

i think so. guys this has been years since i've even thought about rebuilding the bike again until I found this forum. =) So being that I bought it on ebay, probably leaves me to think it was a cheap tawain jug.

I'm picking up the bike today when i get off work. I'll pull the jug and take pictures.




88 Honda Elite
98 engine

[bradthreee]

I have one Polini BBK for sale if you are interested.

PM me

[dem0nk1d]

PM'd what size?

[dem0nk1d]

Here are some pictures of the damage. The bottom ring is still springy. The top ring still has play on the intake side, but is melted into the exhaust side. =)

Head and Plug


---------------------------------------------------------------------------------------------

Jug Exhaust

---------------------------------------------------------------------------------------------

Jug Intake

---------------------------------------------------------------------------------------------

Piston Exhaust


---------------------------------------------------------------------------------------------

Piston Intake

[elitedio]

When I started with my engine, I upped the jetting till it 4 stroked then backed down till it ran clean. Two strokes like to be rich as the gasoline acts as a coolant, I think particularly for break in. I don't like to run the same jetting as someone else. There are a lot of variables including design of expansion chamber, engine compression.

I too am running a Taiwanese bore kit on mine.

Is it possible that your bottom end seals are dried out and leaking?

Super hot exhaust?

I would start with a lot richer jetting. I have not noticed if the OKO carb has different needlejets or jetneedles. If you were at 1/3 rd throttle you were running off the needle and needlejet.

If you haven't you should read some books on two stroke tuning. A copy of the Jennings book is available here at honda spree.

I am sure you will like it when you get it figured out.

[Lunytune]

Taiwan does not necessarily mean junk. They produce lots better than mainland China. I'm running a 50mm overbore (80cc) on an AF16E and doing fine, but still under 300 miles. The AF16 does have split cable throttle and believe that is a plus for the bbk.

It's not always easy to tell from a photo, but your sparkplug looks a little too white to suit me. I suspect you need to upjet, get that plug in the chocolate, or at least tan. I like chocolate. Better too rich than too lean, IMO. Mine is not four stroking so I guess it's okay.

[dem0nk1d]

BTW my kit was from Char-Mo
Here is a link of the kit...
http://www.cens.com/cens/html/en/produc ... 15517.html


Now i'm not to sure if this is different or not, but my head uses a rubber like o-ring and didn't come with the metal gasket, only the paper gasket for the lower part of the jug. Could this been the issue?

The spark plug BTW is brown in color.

I'm starting to think the stock rod might have to much play. I'm going to check clearance today.

[Lunytune]

Yeah, photos can be deceiving. One looks too light, the other indicates chocolate.

Two things. Never heard of a rubber O ring for the head. It should have been metal. In the photo of the link you sent, the kit has a metal head gasket.

Also, the link indicates kit is for AF24 (DIO SR). You have this on an AF16 Elite? I have a DIO SR but nomenclature says it has AF18 powerplant on AF28 chassis. Since I can't find VIN, I have no idea what year it is. I know there is some interchangeability with the AF16/AF18 and would like to know more about this AF24. I'm totally unfamiliar with it. I don't think that is an issue though, for you. Unless there may be some mismatch on the ports. But if that was the case, I don't think you would have the power you indicate.

[Wheelman-111]

Greetings:

Some bore kits eliminate the head gasket by means of a Viton or Teflon o-ring that can take the heat. Increased compression and the ability to dismantle without replacing the gasket each time are the advantages. The head and the cylinder have to be dead-flat.

The Kit photo may be a generic one - not representative of DK's exact item.

[dem0nk1d]

I was just used that picture from the vendors site to show you guys what the kit looked like. Minus the metal head gasket. Mine didnÔÇÖt have the metal gasket but uses that orange o-ring as you can see in my pics. Also the two shots of the spark plug / head is the same unit, just different angles. Also as I was reading about spark plug color in 2-strokes should be brown in color. I could be wrong.


So you guy still think it was running lean? We can all agree it ran way to hot on the exhaust side.