Yamaha Jog CS50 Commuter

[geoffh]

I travel to work every day hail, rain, snow.but mostly dry and pleasant.It,s just five miles there and five and half back takes around twenty mins.The traffic gets up to around 35mph so I like to keep up, this is how I like to do it.

One Yamaha Jog CS50 2004 (been parked up for long time before I got it)
take the restrictions out it cos 30mph is dangerous
fit a Naraku Traffic exhaust
pop in a Polini Hi speed variator kit

Result 30 to 35 quick enough,44 tucked in down hill,I,m 190lb with wet weather clothes and kit bag.
That's all I,ve done,no orange bit,s, empty tins, racing stickers,kevlar belts etc etc

Don.t get me wrong it,s not been plain sailing over 8 years I,ve had some issues, 4 walk,s of shame 1 engine scrapped 5 barrel,s that are door stops now.

Many thanks to all who have posted on this site.   

  This my old 2005 in it,s sunday best,sold on but missed

 This is my (new) 2004 current ride 9374 miles on the clock,so many more to come I hope

I know this model was not available in the U.S.A but it uses the 49cc minarelli AC engine so my set up should transfer to other models for a gentle and long lasting(I hope) commuter scoot. 

[geoffh]

Whoope,It,s spring early summer here,time for testing,easy first step fuel comsumption,18.5 mpl or 80mpg(uk)or 70mpg (usa).The speedo on the scoot records maybe 10% over reality so bear that in mind.
Next up The Speed Test.My sat nav has a trip monitor which is very accurate (tested against my trucks tachograph)

Six runs down a 3rd of mile flat (ish) road and no other traffic, scoot warmed up, a little head wind so street lamp to street lamp and then power down.WOT=wide open,force=my version of trying to tickle the throttle for best results,Tucked,yes it works but it,s not comfy.
MAX AVE DURATION
WOT1 39 25 25sec
WOT2 37 22 31
FORCE 39 23 32
FORCE 37 22 32
TUCKED 40 24 21
TUCKED 37 26 26
0 to 30 9sec to 15sec Cheers geoff

[geoffh]

Well here we go, the jog had started to fade a little,just a tad but enough to make me wonder what was going wrong.I decided to replace the Yamaha belt (just on the service level)for a new one and for good measure to replace the britle air filter assy.Replacment parts sourced from a firm I,ve used before with no problems.
I made the mistake of fitting both parts at once and went for a test run,oh boy she flew (scoot)for 1/4 mile then suddenly the engine sputtered and felt like it had run out of gas,nursed it home and checked my work, all good.I noticed that the chinarelli intake snorkel was 50% larger than the Yamaha original so swapped out the carb to air box hose (duct taped to seal)into my old filter and all seemed fine on the stand.I,m sure I had a soft seize due to a lean mix,checked the plug lovely tan color and left it at that.Nope still not right missing some umph,put it down to the new air mix and ran it for my trips to work for a week.Pondering the problem I made a to do list and slap bang up there was "try old belt" turns out the Yamaha belt is 738 X 16.5 the new belt was 750 X 16.5,I replaced the old belt and the umph returned,deep joy .I,ll start a thread in scooter chat about unhelpful, ignorant, lazy, workshy suppliers who sold me the wrong belt.

geoff

[AtariGuy]

Dumb question, you said you used the naraku traffic exhaust, what did you think of it's sound level and did it open up any additional performance swapping into it?

[geoffh]

Atariguy,It,s been a long time since I first fitted it but as I recall about 5mph better than the standard aftermarket silencer,hard to be precise about the noise a tad louder than standard but nothing like a regular power pipe.I leave for work a 6.30 am in s residential area and it,s no louder than any of the cars around us.I,ve been using this one for 5 years and still going strong.Highly recommended.

Geoff

[geoffh]

While I,m here confession time,for a long time I ran the scoot with the needle clip one step lower than the middle clip,I think I got that "tip" from a 4T U tube clip.This made the scoot hard to start when warm but as I go directly to work leave it for 8 hours then repeat the trip it never really bothered me.After a winters worth of Brent,s how to videos I,ve seen the light and I,m not using a plug a month any longer.

Con 2,somehow I missed the "check and grease" torque converter from my 2T education.A tribute to the scoot that after 9000miles and 13 years it still had a smidge of lubricant in there.Oversight retified I,m hoping to test tomorrow but it does perform better in traffic, down hill the speedo went over 45mph but the GPS will tell the truth.
Cheers geoff

[geoffh]

Ooop,s bad day at blackrock,I fitted a new drive belt today and went for a spin,I,ve also just got a "tiny tach" and over the week have been clocking my engine,up to fitting the belt I,d seen 6500rpm mostly now and again 7000rpm happy days.After fitting the belt it got zippy,long straight 7100rpm 7200 rpm and then bang seized up,long walk of shame,here,s the piston.

geoff


 so what do you think,bad fitting,cheap nasty parts,cr""p mechanic,to fast,I,m still on auto lube,rebuilding in the morning so your thoughts will count.

[spaz12]

A little lean on your main jet, but from what I don't know. Could be jetting, needle or even an air leak that gets worse as it worms up. Get yourself a CHT gauge if don't already have one.

[ryan_ott]

Scoring on intake and exhaust, lean mixture, lack of lube and high egt. That piston also looks well used. Rebuild bigger and better. Make sure your auto lube pump is working or premix.

['O'Verse]

Drop the autolube. Go premix.

[gsx600racer]

Iv looked at both pics,

In the first picture, the side shown is the side that would be closest to to the fan and would be cooler by default seeing its seeing fresh/cool air first. There is very little carbon on the rings(where they go into the grooves) as well as between the rings on the piston and also below the bottom ring.

The second picture, this side is opposite of the fan and gets cooled last. Carbon build up on the rings, carbon between the rings, and more carbon below the bottom ring.

This is very clear this engine was running hot before it seized. I am on the fence as the lack of oil being part of the issue with all that carbon on one side. If if the whole piston looked like the first pic, then I would consider it.

Depending on the cylinder, as long as is not any major grooves, clean it up give it a re-hone just replace the piston, rings & wrist bearings. I bet wrist pin is blue/brown as hell from the heat.

On the piston, was there a lot of burnt oil on the underside of the dome ?

PS, I second premix

[geoffh]

Thanks all,I,ve got a new barrel and piston in the stores,I,ll rebuild, get her going,then go pre mix and upjet a little.And yes there is burnt oil under the crown and the wrist pin is brown/blue.I,ll post pictures after.Once again thanks.
Geoff

[geoffh]

Well that went well,we are up and running,I,ve gone back to my old air box set up and will keep the RPM at 60000 ish for a while.I,m thinking the engine was running lean and the extra umph of the new belt tipped it over the edge(and a greedy rider pushing to far).I,ll gen up on pre mix and update as we go.

Hi ho, Hi oh, off to work we go

geoff

[geoffh]

Hi ho.oh no,3 miles in and a soft sieze,left her for dead and got a lift to work,then pushed it home on the hottest day of the year so far,done a rebuild and gone premix with an 86 main jet for good measure,running again,trial by commute in the morning

geoff

[geoffh]

Did,nt get far on that set up,500yrd cut out so parked up and took the car(one full hour of frustration and traffic jams)swapped out the 86 jet back to the unknown clone jet,It,s up and at em again,2 days of commute so far I,ve kept the revs down around 6.5 but it,s hard to swap from WOT to gentle George but needs must until I sort the pre mix out,the plug is black and ashey but still going,keep you posted.

Geoff