X8R engine racing at start up and other issues

Hi guys,

Thanks for previous help with dodgy headlights, didn't post a follow up as have stayed working after simply dismantling and reassembling everything. No obvious fault found.

Now new problems, our son got his CBT and went out for first time. He did a couple of miles then on the way back the scooter died. After standing it started OK again and he rode it home.

I took it out after for a test ride and it stopped 5 or 6 times on full throttle. I suspected the vacuum tap as a possible cause because on letting it stand for some time I was able to ride it back on half throttle.

Looked at the vacuum tap today, it seems to work fine with a really good flow of fuel when vacuum was applied.

Oddly though the bike is now racing like crazy when started, it sounds practically like full throttle is being applied and the rear wheel is whizzing round.

I was going to turn down the tick-over before investigating the problems further to prevent the engine self destructing, then realised the owners manual and my general Haynes scooter manual don't identify which screw it actually is.

So, any thoughts on what is up with it, and secondly, which is the idle adjustment screw for this carb?

 

If it's dying on full throttle could be a number of things.
Flooding, caused by the carb float not shutting off when the bowl is full, or too big a main jet fitted, good response upto half throttle then crap.
Then you have the opposite scenario, fuel starvation. Causes are too much air flow, too small a main jet, partially blocked filters. Again great upto half throttle then crap.
Could also be a faulty auto choke mechanism.
Definately sounds like a fuelling issue.
As for racing when started, possible sticking carb slide, kinked/worn throttle cable or fittings.
A few things for you to get started on.
The tickover screw is the bigger of the two on the side of the carb.

 

Cheers Steve,

That gives me plenty to go on.

I hadn't realised before the tickover screw aligns with a hole in the airbox cover, so got that now and you are dead right it's the larger of the two

As I don't know much about the history of this scooter I guess there is nothing for it but to strip the carb and see what is going on.

I'm thinking that maybe it has stood a very long time without running so probably full of varnish and muck. I'm wondering though if the dying issue was perhaps why the previous owner had left it standing... time to open a can of worms lol!

 

Got round to taking a proper look today.

It looks like a badly seized throttle cable is causing all the problems. Scooter was suffering from excessive oiling too before and this seems to have been because the cable wasn't allowing the oil pump to return to the closed position.

The weird thing was the engine screaming seemed to be because the cable had actually disconnected at the throttle twist grip! Quite bizarre. But all in all, new cable, twist grip etc and with luck all should be OK.

I've got the carb off anyway so will give that a clean out too.

 

Nice to see you're diggin in

 

hope it all goes well

 

Thanks for the encouragement

Whilst I'm waiting for parts I took a look at the Haynes Scooter Manual - it says the oil pump (2 stroke) would probably have alignment marks to aid with setting up the cable.

I don't see any at all, it looks like an externally mounted oil pump but all I can actually see is the arm where the end of the cable fits.

How do I set it up? Are there some alignment marks I've missed somewhere, or do I set it up with no free play. Don't want to get it wrong and then have the thing seize up!

 

any pictures?

 

Yep here we go:



On the left of the image is what I see looking down from the top through the storage space under the seat, which isn't a lot because of the exhaust being in the way a bit. On the right of the picture the mirror image is about what one would see if it was possible to look from the front of the scooter at the pump.

I was expecting to see something like a mark on the arm cam and a second mark on the pump body as shown in the Haynes manual but I don't see anything like this.

 

the word probable could mislead, but


I think the alignment marks they are talking about, are the ones on the side of the 2 stroke oil reservoir, there would have to be oil in with the petrol, to set the carb up correctly.

 

Haynes show a picture of a pump where the cam and body both have marks on for alignment, but it is a generic manual rather than one specific to this scooter.

I guess an alternative is that the pump is set to be at max with max throttle as looking at this picture of one from borrowed from Ebay shows there is a physical stop incorporated in the the design:



Not knowing for sure though is a bit of a worry!

 

Sorry Gemma I'm lost,

I don't know why there should be lines to set up a cable, that would be done with the engine at idle, and the tension on the cable set without bias and the grip at the back stop.

send me the bike.........Ill get a better idea

 

can you tell me a little more about the carb if you feel that is the problem, make, model and year, and the bike it is on

 

What I have is a split throttle cable - it operates both the carb slider and the arm on the oil pump simultaneously. The carb is not the issue and I understand how to set that up correctly.

What I am looking for is two alignment (index) marks to set the position of the oil pump when the throttle is either fully closed or fully open. (so the carb is set-up as required then the pump cable is adjusted to the index marks). This ensures the correct oil mixture is supplied for any given throttle position.

Here is the illustration from the Haynes manual:




So the procedure would be to set-up the carb, then adjust the locknuts labelled (B) above until the two index marks (A) align.


So my question is, am I just not seeing the marks on the pump or is there an alternative set-up procedure for this scooter?

 

is this the right and original carb

 

I've now taken off the exhaust and a heat shield to get better access to the oil pump.

I was wondering if these are the index marks (red lines) that need to be aligned?






There is another possible line on the pump body (arrowed with question mark), but it doesn't seem to align with any marks on the cam when it is rotated. Picture shown is of a new pump, the one I'm working with is much dirtier lol, but it is the exact same type.

 

Arr that's better, I think you have found the answer

 

Split throttle cable/oil pump cable setup is exactly the same as on the majority of piaggio/gilera engines. And some chinese scoots.
Easiest way i've found is attach both cables, open throttle fully, (twist grip as far as it will go), see if you can move the oil cam any further open, if you can then adjust the locknuts so that it is fully open and can't go any more, then release the throttle. The cam shouldn't go all the way back to the closed position in my opinion as I am always wary of it not giving enough oil out at idle speed. If you want a bit more oil at lower speeds then adjust the locknuts so that it pulls the cam open a bit at rest position. Won't make any difference to the oil delivery at full throttle, or stress the cable, it just opens the pump.

 

Cheers Steve that sounds like the way to go.

 

I've now got all the parts and have started on the carb strip. I managed to get a Honda manual for not very much on Ebay. After all the questions it turns out

a) I did manage to work out where the alignment marks were, as my picture above

b) aligning them and than adding about a mm extra turn in the 'on' direction for future cable stretch etc, one ends up in exactly the same place Steve recommended, oil pump fully open at full throttle - which is a lot easier than worrying about the alignment marks in the first place