"Doing it Right" or "How to Build a Functional Café Racer"

Sonreir

Oregon
DTT SUPPORTER
Actually... the window of opportunity is probably gone.

If/when you do another rebuild, let the engine warm up and progressively load it. In my opinion, the best break in location is on the track. Let the engine have full throttle and progressively increase the RPMs over a series of runs. Try to stay off the brake and let the engine's compression handle it.
 

teazer

Well-Known Member
DTT BOTM WINNER
No. What you need are revs but no load. Think machining. Too much load and not enough revs hardens the bores and they never seal well.

I'm sure there are more other opinions out there :)
 

Sonreir

Oregon
DTT SUPPORTER
I'm not sure I agree, teaz. The rings don't have a ton of tension on them. You need the compression of a load to help them seat. It's the compression in the chamber that slips behind the rings and causes them to exert force on the walls, no?

Without that load it would be like trying to plug a bathtub with only a few cups of water in it. You need that extra water to cause the plug to fully close the gaps.
 

Quintin Snell

New Member
So, if i read correctly, the general idea is to keep in lower gear and ride around revving the hell out of the engine? Totally the opposite of everything ive been told in the past... i will love that, but im sure my neighbourhood will go ballistic!
so, suggestions here,,, the smoke isnt very much, and only on number 2, do i leave it, or pull the motor again and get another set of rings? If so, can i do just the one pot, or do i do all 4? (I made sure all rings werein the right way up, and in the correct order, just in case anyone was wondering...)
 

DesmoDog

Member
Sonreir said:
Try to stay off the brake and let the engine's compression handle it.
I agree that being too easy on the engine during break in can/will result in the rings not seating well. Been there, done that in fact.

However... the above quote seems to imply that compression causes engine braking. If compression caused engine braking, diesels wouldn't need Jake brakes. Engine braking comes from trying to pull flow past closed throttle plates, which diesels don't have. They have more compression than gas engines, but they don't create manifold vacuum, so they don't engine brake.

If you accept that, it follows that when the engine is braking there's a vacuum in the cylinder. When there's a vacuum in the cylinder, the rings aren't getting pushed against the cylinder walls from combustion pressure like they are when under power, so I question just how much engine braking contributes to break in.
 

datadavid

New Member
Re: "Doing it Right" or "How to Build a Functional Café Racer"

Quintin Snell said:
So, if i read correctly, the general idea is to keep in lower gear and ride around revving the hell out of the engine? Totally the opposite of everything ive been told in the past... i will love that, but im sure my neighbourhood will go ballistic!
so, suggestions here,,, the smoke isnt very much, and only on number 2, do i leave it, or pull the motor again and get another set of rings? If so, can i do just the one pot, or do i do all 4? (I made sure all rings werein the right way up, and in the correct order, just in case anyone was wondering...)
4? So you are not talking about your cx anymore?
 

teazer

Well-Known Member
DTT BOTM WINNER
Too many revs or too much load too soon is bad. Progressively increase the load but use the whole rev range. If you run it too light on load and too low revs for very long it will never bed in.

Agree that the track is a good place to bed it in. Compression braking/engine braking just means shutting the throttle and letting the engine slow you down.
 

Quintin Snell

New Member
Re: "Doing it Right" or "How to Build a Functional Café Racer"

datadavid said:
4? So you are not talking about your cx anymore?
Nope, i also have a Gs1000g which i rebuilt, and the number 2 piston still has some intermittent smoking. Not bad, but after that much work, there should be none...
 

DohcBikes

Fuck You.
With a fresh rebuild, assuming already that everything is properly assembled, pre lubed, and has arrived at operating temperature while slightly above idle to build and maintain oil pressure:

-Never rev a new engine with no load on it.

- It is cylinder pressure that forces the rings into shape, and the piston travel that matches them to the bore. High RPM under load is the best way to achieve even cylinder pressure and high piston speed.

- after the engine is warm, you need to get to it. Be ready to ride, accidents can be more likely when focusing only on the task of seating the engine components at high rpm, road hazards still exist. Have a place to ride it like it needs to be ridden, a track if possible. Firing it up and whomping it up and down your block is dumb.

-Safely enter a rural highway or track. Briskly throttle and get out of first gear, take it to a grand under redline through second, third, and fourth gear. You dont want to be in the lower rpm when you get into the next gear up, get those shifts made quickly.

- At a grand under redline in fourth, let the throttle snap shut and roll down through the rpm until it gets to a safe rpm to downshift, repeat through third and into second. Using no clutch to downshift is recommended.

-After the initial runup, go WOT to redline through as many gears as you can without endangering yourself or others. Do not miss any shifts. Let the trottle snap shut, roll down through the gears safely to second, and repeat.

Your engine is ready. Go ride it however you want to now. Run it the way you want it to run.
 

crazypj

Split personality, I fake being smart
I warm up 'new' motor at 2,000 rpm to make sure the oil is being thrown everywhere it needs to go, minute or so at first start isn't so bad as there will be assembly lube on all moving parts
Too much idling is really bad though, usually causes problems with small end of connecting rod which tends to 'go dry' and scuff and/or have partial seizure (seen it many many times)
I also chamfer the bottom edge of piston thrust face to direct more oil inside piston (rather than have the factory square edge)
I think it also helps cool piston crown?
Not as good as real oil jets but better than nothing ;)
I think it may have been mentioned previously, it isn't a good idea to slather oil all over piston, rings and bore as your much more likely to get glazing of rings and cylinder.
It will bed in eventually but can easily take 20~30,000 miles
I use only a tiny bit of oil on piston skirt thrust face and a smear on the front below rings
 

Tune-A-Fish

BOTM LOSER Proudly Deplorable
I don't know how a cycle motor off the showroom floor ever gets past the first 1K miles with all the stoopid furkers ridin em ::)

The definition of torque is when you push down on a boner your feet come off the ground ;D

Yup that's all nothing to add... great stuff here though and I learned a lots :eek:
 

crazypj

Split personality, I fake being smart
In the 70's Honda made a films of bikes straight ff the production line being run through the gears and taken to red line before being dismantled and shipped
The main reason for 'break in' period was/is to try and get new riders used to new bike and it's foibles rather than a chance of engine damage
 

Sideswipe

New Member
I always wondered about the 'ideal' break in process - but without any tracks nearby I'd be concerned about running it through very many gears to redline!! :-X
 

Tune-A-Fish

BOTM LOSER Proudly Deplorable
Sideswipe said:
I always wondered about the 'ideal' break in process - but without any tracks nearby I'd be concerned about running it through very many gears to redline!! :-X
Leme just say... If you just rebuilt the ZX14... ramp up on the nearest I-? wring it to red through 6th gear your now at a silent cruising speed of about 210MPH... Luckily the bikes computer wunt allow for such fuckery lesst you swapped it out for a race chunk :eek:
 

Psycrow

Member
I will admit strait up I have not read the entire thread YET but I felt it was important to comment on some of the things the OP stated even though it was 2012 he made many great points and responses have added may more and I whole heartedly support the positive tone his post took however I have a big issue with one of his main points. I seriously think the definition of "Cafe Racer" needs to evolve somewhat.. cafes racers of their day were brittish twins modern in their own time and cut and modified to remove the unnecessary and mod the essential for maximum performance. If we apply that to today it would be doing the same to a late model GSXR.. if your going to extend the term beyond its origins an include 70's and 80's UJMs then you can't apply other rules to the term either. What am I going on about? The attitude that if you don't over bore and port and polish your doing it wrong... I am getting so sick of this attitude and it's what keeps me from certain other boards with Cafe in the name....I strongly agree with function over form and the importance of making a bike mechanically sound before dumping money into esthetics HOWEVER.
Even with mechanical knowledge sorceing performance parts for these older UJMs are getting difficult. I see no requirement for someone posting a build thread focused on estitics while also addressing mechanical issues. I think it's okay to take an old ugly bike from the past and keep it on the road and current with trends of the time and not chase some idea of performance that will never be achieved by the standards set by today's bikes. If someone takes a runner and tunes it up replaces worn parts and rotting rubber then starts making it look trendy where is the problem? Please do not look down on these people or call them less because they can't afford or have the desire to chase HP... can't it simply be a cafe because of the style the bike is aspiring to?

Psy

Sent from my SM-G903W using Tapatalk
 

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