Yamaha xc125 (riva) Trouble Shooting

Hawthorne Swan-Scott /

Today I picked up a beautiful 1988 Yamaha Riva (125cc) for a pretty good deal the owner said that it was running within the last week weeks and he guessed it went bad something to do with the fuel system.

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I took it to make and replaced the battery to find all the electrics works was reliving, I tried to turn it over after filling it up with fresh gas and oil to find it wouldn't kick over to start. I took apart the airbox and took a look at the hoses running from the petcock to the carb and everything. And after taking the carb apart it found that there wasn't any gas in the float bowl. I am not sure why that could be I know that these bikes didn't come with fuel filters so the carb could be clogged. Tomorrow morning I plan on cleaning out the carb and installing a fuel filter. I think that all I need is to clean out the carb I hope but I am not really too sure. Any help would be so greatly appreciated thank you.

Here are the things I have found

1.) One of the hoses running from the tank to the carb still will feed gas when it is trying to start but no other time.

2.) There was a lot of dirt it seemed in the two tubes that split from the bottom of the EVP canister. So I cleaned out the tubes and replaced them, but I am confused as to why two different hoses are coming from the bottom of the canister and thoughts. I know that the canister has charcoal as a filter, but it seems like the entire filter is filled with dirt and mud. I don't doubt because it looks like the owner used it on dirt trails rather than roads. Can I remove the canister all together or is that vital? (if so how can aka like hose and vacuum management?)

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3.) I am not sure about the hose setup there is a very real chance that everything could be attached wrong so I will explain it the best I can.

3a.) First, there is a big hose running from the engine case to nothing but maybe it looks like it should connect to the back of the airbox. Is that hose vital to the vacuum system? It seems to build up pressure if you start it and hold your thumb over the hole. When I tried to start it sounded like there was good compression noises coming from the hose for lack of a better term.

3b.) The Carb has a clear tube running from the bottom of the carb to under the scooter where it can just drip out, I figure that's for excess like a drain?

3c.) One the top of the canister there are two ports you can put the hoses on labeled I and P, right now the hose from the back of the carb is going into the P port and the I port leads through a filter may be to the top of the gas tank. Is this right at all?

3d.) On the back of the carb there are three hoses ports but I am not sure which ones go where. Which hose runs from canister to the carb is the to bottom of the carb?

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Re: Yamaha xc125 (riva) Trouble Shooting

You might be best to visit a Yamaha riva forum .

Re: Yamaha xc125 (riva) Trouble Shooting

The gas is coming out when it turns over.because the petcock opens by vacuum...it will.run without the smog hoses connected..be sure you have a good plug and try squiting some premix in the carb to see if it will try to start

Re: Yamaha xc125 (riva) Trouble Shooting

Pushrod Fifty /

If the gas is flowing to the carb but the plug is dry after cranking, the choke or carb itself or internal filter is clogged.

Re: Yamaha xc125 (riva) Trouble Shooting

As stated many times, this website isn't for scooters. But I did have the same bike which I bought from an auction. I got it running but the airbox was missing and it ran terrible because of that. I took it to a shop and they wanted about 150.00 just to look at it. The mechanics said that bike is known for engine problems and its not worth fixing. It's always worth a try though.

Re: Yamaha xc125 (riva) Trouble Shooting

Pushrod Fifty /

I would clean the box out as best you can and check all hose placements comparing to a parts list or schematic.

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