CB550 Project Scruffy Racer

[Maritime]

OK new bore might need a full re-tune on the idle circuit. Have you gone back to baseline and then done the in and out turns etc after full warm up to re-set the idle?

 

[Sderbyshire]

Yes, i actually had the carbs off and reset the float heights, idle air valves etc

i’m wondering if the inlet manifold o rings i used are too thin and not sealing....

tomorrow ill check valve clearances, timing and try to track any air leak with carb cleaner .....

sure it’ll soon be sorted!

 

[Maritime]

that could be true on the o-rings. depending on who sold them they could be close enough vs exactly right size

 

[Sderbyshire]

Think i’ll take them off and check in a straight edge tomorrow..

 

[Jimbonaut]

Careful with the carb cleaner on your newly painted engine - brake cleaner will work too and won't bugger up your hard work

 

[Maritime]

Wd 40 also works and is paint friendly

 

[Sderbyshire]

Thanks for the leak tracing tips, prob go brake cleaner.

 

[Sderbyshire]

Took off the carbs and manifolds earlier to check out the o-rings.

i fitted o-rings from my ‘selection box’ in the workshop not original Honda ones..... and maybe i went a size too small.

original spec is 30.8 x 3.2, i had installed 30 x 3.5
swapped to one size larger this morning , they do fill out the grooves better and protrude further so am hopeful they will seal better.

rebuilt and Scruffy started straight up and idled well, but did rev up quite a bit as the engine warmed.

i’m not sure there is anything wrong now, the motor needs to be run in and then tuned properly

unfortunately its freezing here and we are in lockdown so i can’t really get Scruffy out

maybe we could go for an essential trip to the shops, for Beer

 

[Sderbyshire]

Managed to get Scruffy out for a short test ride.

added some fresh fuel then had a short ride running the motor on and off load 3-5k revs

Scruffy is significantly more torquey than before the rebuild

the motor pulls from about 2500 revs and is definitely more powerful

testing was very limited but i’m calling that a success!

next i’ll check and reset timing/valves and work on the idle which isnt right still

Steve

 

[Jimbonaut]

Here in Montreal all non-essential shops have been closed for months (like everywhere else). Beer and weed shops? Essential. Montreal's not so bad.

Congrats on the first shakedown, good luck figuring out that high idle. Sorry if these are all redundant suggestions but did you vacuum synch the carbs? Mixture screws all synched? Not sure if your mixture screws have them or not but may there be a missing washer or o-ring on one or more of them? Are you sure all the jets have the right size holes? (I sent a year trying to figure out a carb situation on my KLR - turns out a PO had bored one of the jets so what I thought was a factory OEM jet size was most definitely not)

 

[Sderbyshire]

Thanks for the suggestions James
i’ll report back in the week after i reset the valves and timing and do a vac sync.
i replaced all the jets previously and Scruffy was running well.

 

[Jimbonaut]

I bought one of these from the UK -

https://www.carbtune.com/colortune.html

ColourTune - it's like a spark plug but with a window into the combustion chamber. Great bit of kit for dialling in the mixture based on the colour of the explosion - bunsen blue indicates a correct mixture of gas and air.

 

[Sderbyshire]

Good idea!
i’ve known about those for decades but never bought one.....

 

[Sderbyshire]

Its snowy here in the UK at the moment , and we are still in lockdown, so thought i’d rebuild Scruffy’s carb bank to use the cleanest components from the two sets that i have

when i built the working carb set i kept as much of the original setup as possible just to get Scruffy running.
now i’m looking to make the rebuilt bike/motor look as good as possible, while retaining originality

so here’s the rebuilt carb bank with the old rusty linkage in the background for comparison :-O

 

[Sderbyshire]

Small Sruffy update this weekend.

bike is in one piece and running well, but with lockdown and terrible weather i’ve not run the new motor in yet

i have borrowed a carb balancer and might do that today, in the meantime i thought i’d attempt to tidy up Scruffy’s ‘Honda’ tank badges.

there were chipped, bent and generally scruffy.... but rather than replace i thought i would try :

cleaning and flattening them
applying an all over black paint
sanding the letters back to a brushed aluminium finish

it went well !

The finished result is’nt perfect, but thats just right !
if i wanted perfect i’d buy new not restore
Steve

 

[irk miller]

They look perfect from here. Loving this orange paint.

 

[pidjones]

Looks great! When balancing, let Scruffy warm up fully first.

 

[Sderbyshire]

Looks great! When balancing, let Scruffy warm up fully first.

Yes, thanks

i’m still having hot idle issues so didnt get to balance the carbs.

as scruffy warms up the idle deteriorates

i’m thinking either too rich a mixture or perhaps an air leak is opening up, but i cant think where!

i do wonder if i set the valve clearances a little tight, as its very quiet, could this cause such an issue as the bike gets hot?

Otherwise Scruffy is transformed by the engine work, really torquey and powerful up to 7k, not tried more yet.

 

[irk miller]

If the valves are too tight, that would certainly show it's head when hot, as things expand. That's why we measure gaps.

 

[Sderbyshire]

If the valves are too tight, that would certainly show it's head when hot, as things expand. That's why we measure gaps.

Yes, i did measure the gaps carefully but am wondering if i erred on the side of tight would this cause hot idle issues?