Project XL185/CG250 swap

[XLsior]

The tapered fat bar arrived yesterday.
I paid $51 AUD shipped from Ebay...the kit included the bar, grips, bar risers and foam pad.

The bar is definitely a step up in strength/material quality over the cheap chinsy noodle bar it's replacing.

The grips appear to be genuine pro taper pillow tops.

bar risers would have worked for a 22mm to 28mm conversion, but I am not using them.

The foam pad won't be used either.

However the whole package shipped represented better value then some handle bar only options.

A bit of a faff making the swap and had to use the dremel* and shape the bark buster clamps a bit to suit the bar taper.

Still got to dial in the adjustment/position but a definite improvement overall.

[XLsior]

CG198/148.5mm pushrods arrived.

Went in no problem with valve adjustment to spare.

A bit chonky compared to the orginal pushrods...

Put it all back together with a drizzle of oil on top.

turned over fine without spark plug...so no valves kissing piston.

Replaced spark plug and a definite bump in compression with a pronounced "thomp" sound.

Starter ran out of juice before it could fire...And my right knee isn't capable of constant kick start attempts with the new found compression...

Battery is on trickle charge...Also got a new direct fit* LED headlight to try over the stock P15 candle.

There is palpable anticipation/anxiety with the shade tree poolnoodle performance big bore job...The compression is reassuring but I also still have doubts about the headgasket and mating surfaces.

[XLsior]

Ok I got the bike running on high idle...2000rpm in neutral.

was sounding fine and the bike got up to temp...then it starting sounding harsh in the top end and then the revs start going down and then the bike cuts out...

Still turns over and restarts fine but the slow down and cut symptoms are repeatable...

I cant do much while the engine is hot. I am wondering if the cam rollers are sticking at running temp...is my first guess.

There were installed in correct arrangement with the spring washer on the piston side...

Its my only explanation for the rev drop and konk out.

So chalk a point to the big bore and gaskets working working...and take 2 steps back for the valve train...I believe.

I'm hoping the head does not have to come off again. But I'm thinking it probably will...

[XLsior]

i'm thinking it might be a to small pilot jet creating an overheat lean condition at low rpm...

I wil check valve adjustment since it had time to mesh/bed in with the new push rods tomorrow on a cold engine and bump the pilot jet from its current 40 which might not be enough for the big bore kit.

[XLsior]

Changed jets up 5 on both pilot and main...even though the plug looked rich.

Checked valve lash on cold engine no notable change.

cranked engine without plug seemed fine.

Put it all back together and got the bike running.

As soon as it get to a certain temp (nothing to indicate an overheat) and then there is a sluggish binding and the engine stalls and is hard to turn over.

I'm wonder now if i might have installed the rolling cam followers 180* aka back to front and if that might be causing an issue with heat bind otherwise the only other explanation I have is the piston is expanding larger than the bore...

Unfortunately this means the head and jug need to come off again...

But other than that the bike for a few brief minutes runs great...

I've got an inkling the cam rollers are the issue.

[XLsior]

I'm getting pretty good removing the cylinder now...

I wanted to inspect the big bore cylinder and cam rollers for any galling/witness marks.

So uninstalled it all again...

There was a small scuff mark near the inner skirt base where the piston is making contact before/after BDC.

There was also a tight spot between the roller cams...

No witness marks on top of piston or valves.

But nothing suggested to me there was major friction heat and galling to cause the engine to stall out.

I reinstalled the original flat cam followers into the big bore cyllinder...

The follower holding center pin appear to be longer with the new roller kit and would not fit into the standard 67mm cylinder, but does in the big bore....

However I installed the shorter pin for testing.

Swapping back to flat cam followers turns out the push rod length isn't majorly effected between rollers and flats maybe 2mm so rollers should be fine with a stock CG250 configuration...other than the holding pin length issue.

With the flat cam followers the head/cylinder DIY skimming also meant the standard push-rods were to long... and the CG198 push-rods are borderline to short...but for testing purposes they were installed.

Kickstart was always stiff/locked when fully assembled, but fine with no cylinder

Anyhoo I got it all back together a and went back to 40/130 jets in the PE28.


The engine fired up on E'start and began to run albeit a bit tappet clackety....

got up to temp then started to bind and stall out.... /ughh

restarted again...and rev'd it hard 4000rpm for about 5 sec hoping to self clear any tightspots...and the bike just kept running at idle for a good 1-2min...a somewhat sigh of relief as I think it broke passed its breaking in tightness...

BUT...I think i will have to take it apart again and retry the roller cam followers due to the shorter push rods on flat cam followers being to short (And perhaps they might help quiet down the valve train)...

Will have to wait for tomorrow when the engine is cold again...

For a moment I felt like I would have to bin the bigbore kit...but I think there's still a pinch of hope now...

[XLsior]

Awoke a perfect weather Sunday morning...

Had the cylinder out roller cam followers back in as was the 1st install configuration...

Put in a 42 pilot jet as a bump up...

nipped the bike back all together again and was ready to ride after lunch.

I decided to ride as hard as required to push passed any stiffness...

Basically had to "just send it" Rode to a friends place for a cup of tea and back again for a hot oil drain.

Think it needs a bigger main jet hitting an rpm wall at about 6600 in 5th and some bog sputters in lower gears pushing WOT Speedometer wasn't reading out either so no top speed runs...

But i guess for those following along the question is; "does the bigbore = more power?"

I can say by my seat of the pants feeling there is a slight to mild improvement. Though its not at the top end...(for now) it wont rip off your arms but there is a tug...

I have heavier cam followers with thicker and shorter pushrods however cam rollers in technical terms should be less friction so its a wash especially on a stock cam profile. Definitely more reliable/durable.

Also
shaved approx 2mm from the cylinder deck and head...roughly.

then the thinner metal head gasket which all bumped up compression as well.

and only the additional 20cc displacement from a 70mm piston over stock 67mm...

Also my stock cylinder was tired to begin with...

Saying all that, I think there is a ever so slight noticeable improvement in power...Is that worth it?...its up to the user, for the average Joe probably not.

Engine braking was definitely better...

I cant say much for top speed because think the main jet was leaning out...

Whatever the power is or isn't I'm just happy it all works hopefully less oil hungry now with a fresh piston and cylinder...I won't be taking it all apart any time soon that's for sure...

[Jjohnson]

Originally Posted by XLsior

Finished seat,

My only insight into the process is start from the back of the seat and work forwards to the tank.

I didn't so ended up with a torn seam at the back and the Honda graphic a bit wonky, trying to redo it just tore up the fabric more as it's held on by jagged tooth cuts in the metal base.

The added foam made it a tighter fit which probably didn;t help with the back seam issue.

Leaving the reskin to warm in the sun or a hot air gun probably would help for those need to repair their own seat covers.

Well what happened next?

[XLsior]

Originally Posted by Jjohnson

Well what happened next?

seating ergonomics were much improved with the foam shave...

handle bar changes also made the overall riding position a natural relaxed state...

before it was constant fidgeting which resulted in fatigue...

[XLsior]

to answer the question can you install roller cam rocker arms on a stock running cam?

answer= Nope

Cam profile is not suitable for the rollers...will sound and perform worse than standard flat cam tappet. Idles like a bucket of bolts and has lost top end rev range.

Which means The cylinder will have to come off yet again...

I have no interest in changing the cam (if i haven't damaged it).

So i will need to get new standard 153mm CG250 pushrods and maybe some enhanced flat tapped cam followers.

Oh well I tried so you guys don't have too.

If you want to install the cam rollers you will need to install the provided cam to achieved a softer 'silence' cam noise (I am lead to believe) However I don't believe it does anything power wise.

The mid range power was fine...but no top end actually worse than before the big bore install...But i'm certain its the rollers.

Spark plug was dry black.

Side note my throttle cable run brearing cover bolt and clear cover plate fell off...so that sucks...

[XLsior]

I replaced the throttle bearing cover by sanding down the slightly larger cover from my cheaper quick twist throttle and found a longer replacement screw to stop it from falling out again...

If you have a similar type throttle you might want to see how long that retention screw is and at least locktite it.

Purchased a folding crate from my big box hardware store and using some strategic holes and zip ties secured it to the rear rack.

The bungee cargo net is from Aliexpress...

Ordered the bits to hopefully sort out the pushrod/cam follower situation...

Just hoping my stock cam in the engine case isn't cactus...

[XLsior]

I ordered some new push rods and these "enhanced cam rockers" They are more or less the same weight than the standards...whether they are any stronger is debatable...

Also got some stainless steel M8 bolts to replaced some of the tired hardware on the bike,

Mainly to replace the rear wheel adjustment bolts..

[XLsior]

Well...

Looks like the pool noodle machine shop might have been a flop.

I took off the cylinder hoping to just changed the rockers and it turns out the piston and cylinder were eating eachother...

Something was out of round and the binding I was experiencing has finally shown up,

I think I caught it just before catastrophe...it did do some distance a high speed attempt and managed to get me home...

But the cylinder kit and piston are cooked. wrist pin required some clearance with the dremel is how much force was in conflict.

definitive hot spot on the cylinder sleeve...

crank and rod seem fine..

Shit happens...

67mm piston and old cylinder back in with new push rods and the "enhanced rockers"

So disregard my Bigbore power assessment as clearly it was running compromised.

I'll wait till the current cylinder starts blue smoking before getting another cylinder kit...

[JerryHawk250]

Oh man! That's not good. I'm wondering if you were getting proper lubrication to the cylinder? That hot spot might be a sign of a poorly cast piston.

[XLsior]

Originally Posted by JerryHawk250

Oh man! That's not good. I'm wondering if you were getting proper lubrication to the cylinder? That hot spot might be a sign of a poorly cast piston.

I'd be more inclined to believe the skirt went out of round, which is not that unlikely considering what it took to make it fit...

as the spot got hotter it expanded more and created more friction.

if you look at the hot spot on the cylinder skirt you can see the propagation point...

a 70mm piston in a 73mm OD skirt only means a 1.5mm skirt wall thickness...So it's prone to deformation...

I gave it a try as an experiment...Still not sure how I feel about the cam roller now....but I'm done with experiments for awhile...