New to forum, mods for a dio

[hughjass63]

Unfortunately, when the bike fell it broke the JDM, if only a small hole. I guess, once my other problems are ironed out, that I will probably replace the unit and wire it up as the original JDM. I am thinking, however, that I would like to keep the luggage rack, so may knock up some sort of compromise.

I have seen quite a few dios for sale since I got mine, but not fetching much money. Scooters in general are not very popular in Australia because of the great distances people often have to travel. However, just over the last couple of years I have noticed several scooter-only shops pop up in Adelaide, so with fuel prices and environmental concerns, Aussies seem to be changing too. Previously I had never seen a scooter-only shop in my life.

[Clivester]

Unfortunately, when the bike fell it broke the JDM, if only a small hole.

Bummer

If only I could persuade my niece in Sydney to wrap one of those cheap bikes and drop it in the mail!

[hughjass63]

okay
the saga continues

I installed the carb reconditioned kit (good buy from keyster), with new needle, seat, gaskets, jets, seals, etc. Reinstalled the carb and the problem remain the same. It bogs down when trying to accelerate or open throttle, but gains power once it clears.

The odd thing is that every time I bring it back to my yard after a run out on the road, I stop to open the yard gate, and as soon as I get back on about 10 seconds later, it takes off and accelerates perfectly!

Have not yet done the plug or pipe clean. (the plugs aren't sold locally so have to go to a specific honda shop.

[bakaracer]

you can get the spark plug from any auto parts store.the plugs for these engines are pretty universal. stock plugs are bp6hs,br6hs,b6hs,bpr6hsa any of those plugs will work. Are you running the airbox or no airbox?

[Wheelman-111]

Greetings:

The NGK BPRs and Autolite/Champion equivalents are not all that easy to find here in Deepinnaharta. One O'Reilly's Autopart store helped me to identify and special-order some 7s and 8s (I think...) one time.

Regardless of whether or not you have an immediate replacement, do have a look at your spark plug to get a clue if it's on the rich or the lean side of "Cardboard" color. I'll predict it's looking a bit dark. If so ride on. If it's light, beware, and maybe add some oil to your air filter element.

Definitely evaluate your exhaust for carbon, especially if the plug is dark. With the mileage you presumably have on the scooter, it could be an issue; maybe THE issue.

[hughjass63]

have just tried new plug, and things still the same. also tested fuel pump for flow and there is plenty of petrol getting to carb. I guess the pipe cleaning is next.

this is a wild stab, but could the crank case possibly be leaking? I have noticed a fine spray of black oil under the left of the engine, on the ground below the variator. is there a test for leaking crankcase?

[hughjass63]

have just tried new plug, and things still the same. also tested fuel pump for flow and there is plenty of petrol getting to carb. I guess the pipe cleaning is next.

this is a wild stab, but could the crank case possibly be leaking? I have noticed a fine spray of black oil under the left of the engine, on the ground below the variator. is there a test for leaking crankcase?

[Wheelman-111]

Greetings:

Quoth Hugh:

this is a wild stab, but could the crank case possibly be leaking? I have noticed a fine spray of black oil under the left of the engine, on the ground below the variator.

Uh-oh.
That's not a wild stab at all. Indeed; Aye there's the rub. Bit of a hassle (work...) to remedy but ultimately not too costly unless the crank or the case itself - not the crank seal - is the problem.

is there a test for leaking crankcase?

According to the Service Manual:
1. Start the engine and allow to warm to operating temperature.2
2. Observe for a fine spray of black oil under the left of the engine, on the ground below the variator.

I can't believe this possibility didn't occur to me before, on a high-mileage scooter. Like someone with a serious disease , maybe I was in denial, sorry.

[hughjass63]

Thanks wheelman. I reckon you're right.

I had this sense when I backed off the throttle going down hill like it was struggling to get pressure to draw more fuel in. The possibility occurred to me early on, but I got thinking seriously while I was looking through the recent posts of the guy who is doing a big bore rebuild with heaps of photos and porting (you know, the clean engine guy). I noticed he mentioned a crankcase plug and I thought 'O oh'.

So what would it be? Is the vertical split of the cases leaking, or the main seals, or this crank plug?

It doesn't bother me to remove the engine as I would like to get to the nitty gritty anyway, perhaps even do a bit of porting myself.

I think this is it.

Jon

[Wheelman-111]

Greetings:

It's easy work but time-consuming. Obviously check the case plug/pump seal first and ensure the source of the leak. Were it not for the possibility that your engine has chronically been running lean (because the crankcase may be inhaling air through the leak in addition to expelling petroleum) I'd otherwise suggest you clean it thoroughly, then run it hard to search for the source.

If it's the left crank, everything comes off the block. The Service Manual shows a special Honda tool that assists splitting and reassembling the crankcase, and I recommend you try to buy borrow or steal one. (Kidding about the steal part... - that'd be wrong) I brought pizza for the Dealer's Parts and Service dudes once or twice, now I can have it overnight. The virtue of the tool is that it avoids putting assembly forces across the flywheels of the crank though the big-end pin. Here's why I believe that is important:

Honda cranks are bulletproof-tough in operation, but thet-thar's a press-fit piece through holes in steel discs. I believe part of the reason for Honda shafts' legendary toughness is that they are Factory-trued to a high level of precision. (<.0004mm) This keeps the bearings and seals from having much to endure - the shaft doesn't wobble. Honda-san was a piston-ring maker at the very beginning, and his devotion to metallurgy and Mechanical Engineering Correctness still infuses his products. This is the company that brought us 25,000RPM 250cc Sixes, the CBX and the venerated Blackbird, after all. Correct assembly methodology preserves the engineered-in accuracy - something some brands of scooters could stand to learn. That's why I flinch when someone says they whacked a variator on with an impact gun...

Anyway, the bearings and seals - two apiece - are a a cheap investment protecting the work you've done to split the cases. The scooter will still be cheap overall, considering its purchase price... So is having the crankshaft trueness measured in 3 planes by an experienced Crankshaft Guy or machine shop. The AF16 uses Goo instead of a case-half gasket. Not sure of 18's anatomy, but there's a Service Manual now. Work carefully and Good luck! Let's see some Porting Adventures pics, too!

[hughjass63]

Greetings:
Not sure of 18's anatomy, but there's a Service Manual now.

I found that af18 manual for noizeguy after months of searching. it was like 15 pages deep on a google search.

thanks for encouragement. it might be a while before I start... but I might just get brave.

[hughjass63]

Well, its been 4 months since it all became too much for me. Down on confidence, down on money, down on time. But I've got a few bucks (ie, $100) now so I thought time to be brave again.

So I started up the Dio today.

Just to recap, despite a new piston and bore, carb rebuild, new air filter element and drilled airbox, new variator and rollers and belt, my sk50 dio (af18e) still does not run properly. It seems to start okay, but bogs down as soon as I back off the throttle and try to accelerate again. It then slowly builds up revs, hits the power band again and then goes alright flat out until I back off again.

Wheelman eventually confirmed the most likely problem, a leaking crank. But I don't know where from, although previously I had seen a mist of black oil on the ground under the variator.

Today I removed the oil pump to check whether it was leaking from there. The o ring seemed okay, so I carefully put a bit of gasket goo on the ring but the problem remains. I did note, when the pump was out, that there was fuel clearly visible down the 'pump hole'. In other words, it seems there was a pool of fuel in the crank. It also should be noted that at times fuel comes out of the exhaust manifold (a little black oily)

I then cleaned all the outer cases to see whether it was leaking there. Cannot see leaking anywhere.

So I did a compression test. Using the electric start it takes about 5 seconds to get up to about 92psi. I get the feeling that, if not for a crankcase leak, it should register that compression sooner (after 1 second?).

I dunno. What does anyone thing? Is it the crank seals? If so, why does there not appear to be any fuel leaking from them? I really don't want to do the crank seals unless I am absolutely positive it is them. PS scoot has 24000 km on clock and it is about 17 years old. Would the crank seals have gone hard in that time?

Jon (Australia)

[Wheelman-111]

Greetings:

There won't be "fuel" in the crankcase but there will be pooling oil if the pump is leaking.

If you remove the variator, the Left crank seal is visible. ANY evidence of seepage there is abnormal, and could explain both poor compression and performance. Furthermore, if it leaks fluid out, it probably leaks air in, leaning out your mixture and endangering your shiny new bore kit. The same goes for the opposite end of the crank, behind the alternator.

Yes, seals can go bad, especially if the scooter was started with a pint of oil in the case. Correct seal replacement does involve splitting the cases, and it might not be a bad idea to to that anyway at this mileage. You can try to pry out the seals destructively and insinuate some new ones in. However case-splitting is really not all that hard to do, and the whole process can be performed in an evening. It's probably worth doing just to check the bearings and bottom-end con-rod bearing.

I might recommend the economical way of eliminating the possibility of a faulty pump by tossing it in the bin and obtaining a plug. It can cost as little as $2.17 in US Currency , but VT Cycles sells sells a ready-made one. Then run 32:1 premix and that leaky pump issue goes away.

[hughjass63]

Thanks again.

I must admit I thought the pinkish fluid looked like fuel in the oil pump hole, but you must be right - pink two stroke oil.

It has been a long time since I used a compression tester. Should the compression normally take about 15 rotations of the engine to get the compression level? I somehow remember with cars (from many years ago) that compression was measured in one or two rotations.

Jon

[Wheelman-111]

Greetings:

I bench-tested my compression by jumping the starter to a spare charged battery. 8 cycles should be enough to reach maximum, unless your seals are leaking... Two compression strokes might be enough on a 4-stroke, but I don't believe that it's enough for a 2-stroke. Pressure waves are velocity-dependent.

Using the kickstarter takes longer and depends a bit on how hard you kick. That pressure-wave thing has to work for you. Another reason why faulty reeds will lower the reading a bit.