xl250s engine qu's (cb250rs really)

[pony]

Hi all,

when the top end of the 250 engine (actually a cb250rs engine) starts to rattle, how long do i have left before it lets go? and how does it tend to let go? It tends to rattle at low revs when pulling away.

I'm planning on fitting a larger engine when i can find one, either FT or preferably xl or xr due to kickstart. Do these swap into an XL relatively easily? I know they're a bit tight on space at the top, but i have access to skills and facilities to cover it all.

thanks in advance,

Tony

[AlanH]

FT500 motor goes in relatively easily but is rare as hens teeth and also slightly delicate. Anything else is more difficult and will need work to make fit.

If it's only rattling at lower rpm, are you sure it's not camchain?

If it's not the camchain and is followers then they are in the process of breaking up and are putting metal filings throughout the engine. I've run a rattly RS for 5000 miles without it going bang (I had a spare motor to go in). In the end it sounded like something was chiselling its way out of the top end. Half of a follower was worn away. The cam lobe was pitted and scorched and the cam was eating its way through the head - but it still ran.

[pony]

thanks for the quick reply.

Now i think of it, it could be the cam chain, i just started to get worried having read lots of horror stories. Will that just be the tensioner that needs replacing??

while i have you onboard, do any of the slightly larger XR engines fit the XL250, i.e. XR400, XR350 etc.? Or is the 350 top end compatible with the 250 bottom end??
I think the taller engines (500, 600 etc) have clearance issues with the top tube, but i'm only really looking for a bike that can cruise at 75-80mph and has a bit more poke than the 250. I was thinking 40-ish bhp should do the trick, I'm prepared to do cam, intake and exhaust work, and this is for road use only of course...

suggestions please!

[AlanH]

If it's camchain, the tensioner and chain may both need replacing. Take it apart and have a look.

As for fitting other motors, your 40bhp target is more than a standard FT500 and is probably more than the brakes and chassis are good for. Getting insurance on it would be rather interesting.

You could easily spend £1500 on doing a conversion if you go for a different motor by the time you've bought a motor and all the running gear, made extensive frame mods, fabricated oil tanks, replaced all the electrics, uprated the shocks and front end for the added weight etc. You could get a semi-decent bigger bike for that sort money and it would be more balanced.

So, unless you are particularly wanting to spend a chunk of money on a project to create a loony 250RS, buy something closer to what you need. If that's a reasonable roadgoing single - XBR500 or Yam SRX400/600. The Suzuki Goose 350 is a great little bike. If you want off-road XR400 etc although 75-80mph cruising on a smaller single is not too much fun.

Of course, if you're just doing it for the fun of it and don't mind the costs, keep us all posted on how you get on.

[pony]

Hi again,

and thanks again for the reply. I do kind of have a loony CB250 in mind, see the link below:

http://mulliganmachine.blogspot.com/...-trackers.html

I'm quite pleased with the poke of the 250 for around London, but I'm just looking for a little bit extra for longer journeys. I'd heard the xl/ft 500 engines go in quite easily that's all...

The styling mods will be started in the next 2 weeks, i'll start posting some photos when i pull my finger out of my ___!!

Any help would be appreciated, particularly regarding different engine compatibility!

TBC...

[AlanH]

The only swap I've actually seen is the FT500 and it's fairly tight. I'm sure others are possible as the FT was derived from the earlier XR/XL500. I think the FT motor suffered form dodgy starter gear and it also had no kick start so if an XL/XR matches up then maybe better to go that route. The FT is also a pretty heavy lump considering it only gives 33bhp - still not great on a longer journey.

[MCsanandreas]

good pics on that link,saw a nice 250RS at the Salisbury MAG show last weekend. had one of those little bikes myself a while back but it was a matt black rat!