Topic: Further Adventures of the Missing 6th Gear

[breezy]

You may not want to change out the 34T rear but that's your answer. Putting anything bigger than an 18T in front you will start to grind away at your cases in the front sprocket area. There isn't a lot of optional room in the 550. I just bought a chain and two sprockets 17T front/36T rear) from powersportparts.net for <$100 delivered.

The deal is that a 34T rear is off a 500 originally, the stock 550 came with a 37T rear sprocket and 17T front.  The fact that my gears are low with a 34T rear sprocket is goofy.  A 34T sprocket should make them all higher.  I'll keep the 34T rear and go maybe 20 or 21T on the front.  I'll cut away the cases to make it fit.  Nothing structural where the sprocket rides.

[dave500]

the primary chain is a hyvo type,they all have the same gearing here,so is the engine peak revving nearly at 65 mph?somethings up,,going to way oversize front sprocket isnt the cure,find out whats wrong,maybe get someone else to ride it?

[dave500]

with the bike well hot and ridden,nudge the front wheel up to a solid wall,engage second,then try a high rev drag start,it should stall or smoke the tyre.

[breezy]

the primary chain is a hyvo type,they all have the same gearing here,so is the engine peak revving nearly at 65 mph?somethings up,,going to way oversize front sprocket isnt the cure,find out whats wrong,maybe get someone else to ride it?

My K0 750 right now has a tach that reads about double the auctual RPM, I have ridden it enough to know it is incorrect.  Re-read what trueblue said, I think he is right. 

The tach and speedo readings are immaterial.  The bike is screaming full throttle in 5th and doing 60-65mph.  The clutch isn't slipping, I know what a slipping clutch feels like, this one is solid.  The bike is not under powered, it goes good on accelleration which is smooth and substantial.  Carbs are rebuilt and in tune.

If you are down on power adding teeth to the front sprocket will make it worse.

Power is good, it's that all the gears top out way too early.  It's a gear ratio problem of some sort.  I'll describe more below.

Like was posted if your front sprocket is that bad you will need to replace both sprockets and the chain eventually, because they are usually toast and will continue to wear each other out.

The rear sprocket is like new, the chain is good, laid out on the garage floor, barely perceptible difference between stretched and compressed.  The front sprocket is toast.  That's all that needs to be replaced.

Forgive me if I missed it, but at 65mph is the throttle all the way open or is the tach at redline?

Throttle is all the way open, the tach reading is immaterial. 

NEW DATA:

I talked to the guy I bought the bike from.  He said that he could do 100 in it and that the gear ratios were fine when he got another bike and put this one in storage.  Even with the bad front secondary drive sprocket, he had normal gearing.  So, the ONLY variable, the only thing I changed, is the new tire.  The tire is a Shinko 712R 18" nylon belted.  I stretched a tape measure around it and got 80" circumference which equals about a 25.5" tire diameter.  I don't know how this stacks up against other 18" rear tires, but there is a space of 3 1/2" between the tire and the U of the swing arm, a much bigger tire could fit in there.

[dave500]

so what does your tacho read at 65?recount the sprockets,can you post a photo of them?

[trueblue]

If you have an 18" tyre it WON'T make 40mph difference in top end, I thought for a while I had gearing issues or something of the like with my 650, because mine had plenty of go and felt like it had really short gears, and I believed my tacho for a while which read 9500rpm when it was really doing 5000rpm, and it topped out at just over 60mph like I said a few tweaks which included a new cam chain later and now it pulls hard till well over the ton when I normally back off.  But like has been mentioned here numerous times, THESE ENGINES LOVE TO REV, they don't do well lugging, they do not produce much low end torque like the big vtwin engines but they will sit on 6000 to 7000 rpm all day.  PUTTING A LARGER GEAR ON THE FRONT OR A SMALLER GEAR ON THE BACK WILL ONLY MAKE THE PROBLEM WORSE These engines just don't have the low end power to turn them properly. Now you can either listen to the people here who for the most part know what they are talking about in regards to these bikes or you can go on believing you have a gearing issue in which case no-one here will be able to help you.

[750cafe]

You guys are all wasting your time trying to help this guy!
He is never going to post any pictures and refuses to believe that his gauges are wrong.
He is never going to see if it takes 60 seconds to cover a measured mile at 60mph indicated.
He is never going to replace the sprockets and chain. He loves that rear sprocket and the current chain.
He sounds like he knows it all.     Let him figure out what he is doing wrong.


JMHO,

Eric

[Retro Rocket]

There is nothing wrong with the size of the sprockets or the gearbox ratio's....   The difference between a 34 and a 37 tooth sprocket is NOT 50MPH
Explain why the tacho is irrelevant.? What is it reading at 65mph.? Post pics of the chain and sprockets.

It really sounds like you have no idea and your not listening to the ones that do.

[bryanj]

I agree this man is just not going to listen to the fact that NO GEARING change will lose 50mph and that the main consensus is THE GAUGES ARE WRONG

[breezy]

You guys are all wasting your time trying to help this guy!
He is never going to post any pictures and refuses to believe that his gauges are wrong.
He is never going to see if it takes 60 seconds to cover a measured mile at 60mph indicated.
He is never going to replace the sprockets and chain. He loves that rear sprocket and the current chain.
He sounds like he knows it all.     Let him figure out what he is doing wrong.


JMHO,

Eric

Dude, just chill.  I've been on two wheels most of my life- restored a 52 BSA Gold Star from a basket of parts, a 52' Triumph 6T from a box of parts, Rode and rebuilt a 60 Triumph Trophy, a 72 Triumph Tiger, owned and operated Bat Cave Scooters in San Francisco for 7 years in the 80's- the only Lambretta repair shop in Northern California, now San Francisco Scooter Centre.  I've owned and driven my '58 VW bus for 35 years and have rebuilt 7 motors for it over the years.  I know which end of a screwdriver to hold.  Now get a grip on the following facts:

The Honda clutch is not slipping, period.  I know what a slipping clutch is and I know this clutch is not slipping.  It didn't slip when the bike was put away, it isn't slipping now.
The tach reading is not a factor, the bike is at max rpm at 65 mph
The bike was properly geared when I bought it, the previous owner verified it being rideable with normal gear ratios when he put it away.
The ONLY CHANGE I made was to put a new rear tire on it.  That is the only variable.   If someone would stretch a tape measure around their rear wheel (tape it on there) and give me a number, we can see if that's a factor.

[d9canada]

Breezy, you don't need anyone to measure their tire. You can measure your own and estimate what slightly bigger tires would be in circumference.  Then extrapolate that to difference in speed.  You will find a slightly larger circumference ain't gonna change your top end more than about 10 mph.  In order to knock 50 off the top end, you would need about a 14 inch back wheel.
You could do one thing out of respect to the folks who have been trying to help you.  Take a couple photos of the sprockets.

[phil71]

65Mph at max RPM?
.. how do you know that's the max rpm if you wont tell anyone the the RPM reading?

[strynboen]

how long have you drive soch honda/kawa..or any japanese bikes..this bikes are komplet different then old english  engines..and ww boxer engines
that hitler have seen alive...70 years ago..this 70" hondas go to 10,000 rpm...new today kawas go to  10-20,000 rpm..

[SohRon]

He's running a 34 tooth rear sprocketwith an 18" rear wheel. That wheel is the biggest gear on the bike and the combination isn't helping things. Get the correct rear sprocket and the correct rear wheel, then worry about the clocks. JMO.

[Hush]

Interesting thread for the forum, but everyone please chill.
From my observation of the facts given, Breezy you are running a 34 tooth rear sprocket when the standard 550 rear is a 37.
You have a thrashed out front 17t which could be replaced with an 18t.
Having just done a swap on my 650 from an 18t to a 19t I like this idea a lot for you as the results for me have been unbelievable.
There is a chance that your speedo is giving a faulty reading thereby making you believe the gearing is wrong.
An easy way to check this is to team up with someone else who has a bike and ride with them at a given speed to check yours for accuracy.

[strynboen]

GPS!!!!!!!!!

[TwoTired]

Define -  "engine screaming" in real and verifiable numbers.  If you can't supply this, I'll abandon your thread. 
(Alternately, show the results of your last hearing test.     jk)

Do all the head pipes get hot?  9/10 throttle and 65 MPH IS about right for 1-2 cylinders not working.

I'll note that if pilot jets are working the engine will idle and heat all pipes normally.
If the main jets have fallen out of 1 or 2 carbs (retainer missing), those cylinders will quit working somewhere in the 40-60 MPH range.

Cheers,

[Stev-o]

Get put the popcorn....

[Retro Rocket]

If someone would stretch a tape measure around their rear wheel (tape it on there) and give me a number, we can see if that's a factor.

You are not listening, the tyre is NOT the problem. I have run 16; 17 and 18 inch rear wheels on 22 of these bikes, just like thousands of our members, again ITS NOT THE TYRE.   What is the Tacho reading.?   And how do you know what revs the engine is really doing.? How do you know the tacho isn't working properly.?  Have you ridden beside someone to check your speedo is reading properly.?  The gauges on these bikes are quite often way off the mark..  how bad is that front sprocket.?

[dave500]

can someone go over to brezzys and have a look at this bike?

[Cheffish]

can someone go over to brezzys and have a look at this bike?

+1. Maybe it's not even a 550?

[seanbarney41]

somebody stuck a honda 50 sticker over the old one, but it's on crooked...you, muh man, have one of the baddest ass honda 50s in the world!

[trueblue]

Breezy, I don't care if you built the space shuttle, you obviously know nothing about these bikes.  Old triumphs and volkswagens are nothing like one of these bikes, other than the fact they have wheels attached.  You are going the right way to turn into a typical PO of one of these bikes, someone with no clue on what they are doing, then do a half arsed job of it then blame the bike and sell it on to someone else or worse just park it outside and forget about it. WE NEED SOLID DATA to go by, What is your engine speed at 65mph, use a digital tacho like one on a dwell meter, failing that WHAT DOES YOUR TACHO READ AT 65? IS YOUR SPEEDO ACCURATE? Get someone to ride alongside you and see what their speedo says, or use a GPS.  If you can't start providing some solid data to work off of we can't help you and to put it honestly I have better things to do with my time than try and help someone who is either too arrogant or stupid to listen to the people who are on this board .  Good luck destroying your bike.

[Hush]

So I guess no one is chilling then?
Good point of TT's though, because our bikes make so much background noise with cams and clutches etc, it well could be that it is running on less than the optimum 4 cylinders!
Also the auto advance systems when they freeze/rust up can completely throw a good engine off it's stride, bad/clogged airfilter the same.
Many things to think about on these girls........

[dave500]

breezy thinks its peak revving at 65 mph hush,,i think its out of tune and trying to pull a too tall gear.