Boingk's SDB Enduro Pro 250cc (Aircooled)

[Blender]

Suzuki TS 185's used a VM26 I believe. A good standard carby for around 15 to 20 usable horsepower.

Meanwhile, here are a few happy snaps from Wednesday:

]

Vainly trying to stay ahead of my mate on a very hot CRF250R:



I had him in the corners but he blew past me on the straights pretty easy - mind you if I don't have to rebuild the bike come 20 hours I'll be having the last laugh!

Good fun, no more breakages either. The oil change from 1.5 hours running time looked fairly dirty and had a bit of metal sheen in it as well from the break-in process. She now has 3 hours running time and is going strong. Excuse the helmetless photos!

One thing I have noticed is that you will experience heatsoak if running high throttle loads around a tight track such as the one myself and mates are making. This isn't a problem but you want to make sure you don't overdo it - try and get a low throttle lap or two in before you shut her down or you might overheat the engine and damage something.

Cheers - boingk

nice mate, so it handles well? and to stop that overheating, you get the watercooled one , just playin dude. with the metal shavings, do these engines run an oil filter screen? if so, i would imagine there would be a bunch caught in it. although i have absolutely no idea as to where it would be

 

[boingk]

I wouldn't bother fitting an RM 125 silencer to these, the stock system is quite good as is once derestricted. A CRF or YZF 250 silencer would be more appropriate.

Blender, I appreciate the feedback mate but please don't quote large posts with pictures in them, it clutters the thread something chronic. Can you edit and remove the quote please?

It does indeed handle well, I think its quote stable midcorner and responds to throttle input well by bringing the back out, very controllable. The stock tyres accelerate, turn and brake well.

The filter screen is on the oil change nut (24mm, lower forward left side), very obvious once you undo it as its springloaded and pops out with the nut. Its a mesh screen about the size of your thumb. By 'metal sheen' in the oil I mean tiny, tiny pieces that are more like superfine glitter. That's expected in a new machine during breakin.

Cheers! - boingk

 

[boingk]

At the moment I'm rejetting the SDB after modifying the exhaust - it was breathing through a horribly restrictive arrangement. A 1/4 turn throttle will be going on, to, so should make a world of difference.

The restriction is a plate welded into the exhaust baffling with a small hole, then another smaller perforated tube with an endcap welded into that hole. I couldn't believe it. After some hacking with a hammer and large screwdriver the offending bits were pulled out - they're only tackwelded in. The bike runs but is horribly lean, I am going to rejet the carby when I get the chance, hopefully this week.

More as it happens.

- boingk

 

[boingk]

Standard Jinke mainjet is a 102. Thinking upsizing somewhere in the 106 to 110 range should do it.

- boingk

 

[Blender]

havent got your oko?

 

[boingk]

Nah mate was thinking about it and decided that I may as well do the exhaust and jet appropriately for that first. The thing was breathing through a tube the size of my finger with about 30 holes in it about 3mm diameter each. That's two tenths of bugger all!

- boingk

 

[Blender]

yeah fair enough. from what i hear the standard carbs arnt that bad, but an oko will get the best outta the bike.

 

[boingk]

Yeah they may do, but for now I'll be working the standard. I've got 107.5, 110, 112.5 and 115 mainjets on the way so should be covered.

Also I did the math on the restriction - it gave a breathing area of approximately 200mm^2, whereas a 30mm interal diameter pipe will give over 700mm^2. Enormous difference.

- boingk

 

[Blender]

wow, thats pretty restrictive!
i imagine it would sound different and go abit better with all that xtra flow! let us know how it goes!

 

[boingk]

Fit a 115 Mikuni small round type mainjet, goes like hell now. Note is crisper and fuller but still not stupidly loud. The bike is running well.

I may try a 120 mainjet but will try raising the needle a notch first.

Cheers - boingk

 

[my67xr]

sounds like you are getting close tuning it.

with the oil screen/drain bolt, is it the same as a CB250 bolt ?
you might be able to find a magnetic one, it might grab some of the finer metal filings etc thats mixed in with the oil?

have you had the exhaust header pipe off the head?
the Honda's were known for having more weld inside the pipe than what was needed.
a clean up of the welds inside the pipe here with a Dremel and carbide grinding burr or the like can do wonders too.

 

[boingk]

Nah haven't had the pipe off the head yet, may in future.

The 115 mainjet rides alright but could use upping to a 117.5 or 120 I think. I will do that when I get a chance.

For the moment the bike is out with sheared rear sprocket bolts. I would highly suggest anyone with these bikes replace these bolts ASAP as they are very weak and sheared simultaneously.... interestingly it happened first ride after the mainjet/exhaust mod.

Cheers - boingk

 

[boingk]

For sale, pickup Goulburn NSW.

Total runtime app 10 hours, oil changes at 15min, 1hr, 3hrs, 5hrs and 10hrs. Valves in spec, exhaust restrictor removed and mainjet increased to 115.

All linkages and bearings greased and inspected before assembly and again at 5hr mark.

Runs and rides very well.

Asking $1200.

Only selling because I bought a road regoed dirtbike and don't own a trailer.

Cheers - boingk

 

[my67xr]

you might want to delete that post above, and put it in the right area
http://www.miniriders.com/mini-classifieds/

otherwise the mods will delete it


here is a copy of the required layout too, copy and paste it into your classified ad

ITEM AND CONDITION:


PRICE, PAYMENT METHODS AND TERMS OF SALE:


REASON FOR SELLING:


EXTRA INFO:


LOCATION AND CONTACT DETAILS:


PICTURES: