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Discussion Starter · #1 ·
Sleds starts easily and runs great right up to 7500 then bogs out for a few seconds and then eventually pushes through the bogging and once it hits 8000 it runs strong...as far up as 8500. Once the rpm drops under 8000 it iwill bog again. If it is on a stand running, it will not push through the bogging, it igets to 7500 ish and just floats up and down a bit around there.

This has been around for about 5 full tanks of gas. Took it to the only good shop around and they spent 1/2 day on it and couldn't find the problem. Folllowing is a list of the things we have tried.

- new plugs
- swapped MPEM with other good running sled
- cleaned and verfied operation of RAV valves
- replaced voltage regulator
- checked all error codes and no problems showing on shop computer while problem occurs
- fuel pump pressure checked and confirmed good
- changed primary clutch spring
- changed clicker settings
- checked and added grease to various electrical connections

I was suspicious of the fuel injectors for a while but the fact the it runs so strong at 8000 rpm and up combined with the guy at the shop telling me that fuel injector problems are very rare on this sled we have sort of ruled that out.

We live at 5000ft and ride up at 10,000ft it will do it at any elevation.

Don't know where to look next.
 

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A couple of things to check when this happens is the air/fuel ratio and EGT. The AF with be an average of both cylinders, and the EGT will show the level of unbalance between the two cylinder. Another thing to check is what rpm the ERAVE open.

As for the injectors, they are from the auto industry which have proven reliable. However, debris from storage finding its way in or past the injector basket filter is common. The injectors in operation get cooled by the flow of gas, so if there is a restriction then it could leave the injector to run hotter and eventually cause a fault. Injector flow tolerance is 6%.
 

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Discussion Starter · #3 ·
Thank you Daag44,

Is the AF ratio something that can only be read on the shop computer or can I do it with some sort of measureing instrument? Since it was not an easy fix they have now put me in a 3 week wait line.

I take it from you comment that there is an Exhaust Gas Temp sensor for each cylinder? Do you know if this a 4-20ma signal or resistance or 0-10V, is there a way to read these values with a good mulitimeter?

I was thinking this morning of trying a timing light to see if i could tell if i am getting consistent spark when it is bogging at 7500 rpm but I suspect that will be too fast to see anything.

The RAV are opening around 7200, opeing at the same time. Shop guy said that was right.

Certainly need to determine if it is a fuel delivery problem or a spark/spark timing problem.
 

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The Air/Fuel is measured with a Wideband which is simply an O2 sensor like in your car but with a wider range of values. AEM makes two that are affordable. $225 CAN + shipping for the base model and $425 + shipping for the model with a data logger and a better viewing screen that works excellent for day viewing. Much cheaper in US dollars and both will work. The key to driving safe with a Wideband is a video cam pointed at the gauges. It is that bad because you really see what is going on with fuelling and it takes all your attention away from the trail. They should put a big warning for sled usage.

Budget is always an issue, so before getting the Wideband I would consider a few other things, but keep some spare change in the budget in case it becomes too difficult to troubleshoot. Money spent at the shop will easily cover this gauge. My personal thought from experience is you should own one eventually, even if its just for pre-season troubleshooting and the cost is shared among your buddies. It's simply a phenomenal tool for diagnosing tough to find problems. But don't get too exited at this moment because money needs to be spent on more basic tools. I'm talking little money, but it adds up.

Before going further, a few things about your experience with the sled and some basics would be helpful:

1. Was it working fine last season?

2. How many seasons have you owned it?

3. Any problems in previous seasons that needed to be fixed?

4. What rpm does it idle when warm?

5. Is battery voltage showing 14.5 Vdc at idle and above?

6. What type of work did the shop do so far:

- TPS reset?

- Check fuel pressure?

- Replace battery?

- Change fuel filter?

- Replace any sensors?

- Adjusted idle?

On #6, please note that I'm not suggesting what the tech should have done. I am simply listing a few examples or common things that may have been done. 30 min is not much time to work on a sled, but a great deal can be done nonetheless if the tech is efficient. For example some techs avoid resetting an old TPS due to the possibility of false value when the throttle is sitting on the zero stop and they would have a point. That's actually where a Wideband comes into play with an instant picture of a lean condition.
 

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Thank you Daag44,

Is the AF ratio something that can only be read on the shop computer or can I do it with some sort of measuring instrument? Since it was not an easy fix they have now put me in a 3 week wait line.

On the bold, this is great news!!! I am hopeful you get it worked-out in the next few days. The chance of this depends on the answers you give to my previous post. For example if you tell me you had nothing but trouble with this sled, then....well....ahhhh...lol. My guess is it worked find last season.

I take it from you comment that there is an Exhaust Gas Temp sensor for each cylinder? Do you know if this a 4-20ma signal or resistance or 0-10V, is there a way to read these values with a good multimeter?

Sorry, not EGT with stock sled. Depending how far you want to go, you could get one. But everything I do on this forum takes budget and the owner into consideration. I am used to everyone wanting to know something different about their sleds, so I go with what the owner wants to bring to the table. Some have had mostly great luck and want to just ride while others have ridden with enough problems that they want to take a few steps further.

I was thinking this morning of trying a timing light to see if i could tell if i am getting consistent spark when it is bogging at 7500 rpm but I suspect that will be too fast to see anything.

Putting a timing light on a two stroke is always a great idea for various reasons. I don't think it will help solve the issue at hand, but one never knows.

The RAV are opening around 7200, opeing at the same time. Shop guy said that was right.

How did he see the ERAVEs of both cylinders were opening at 7200 rpm? Is there a 3/4 hole in the black cap to see them opening?

Certainly need to determine if it is a fuel delivery problem or a spark/spark timing problem.

Unless there was something torn apart and/or it was having trouble last season, chances are it is a fuel delivery problem that will be very easy to troubleshoot and fixed. 95% of SDI problems are easy to find and fix. The trick is knowing the weaknesses and most common problems.
 

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Discussion Starter · #6 ·
Thanks again for your help.

History....bought this sled and another one just like it new for my sons from a dealer in 08. Only had a few minor problems, except for this one they have been really reliable sleds. Having a second sled of the same is nice in that i can switch parts that are suspect to see if a part is faulty without having to buy each item.

The problem actually showed up 3 years ago, it just showed up mid way through the season, no accident or other problem associated. Probably 5 tanks of gas were ran through the sled after the problem arose. Sleds have been in storage while sons were away at college the last 3 years, fresh gas and battery kept on a tender. The sled is running now exactly the way it did when it was last being ridden. At all RPM's except between 7500-8000 it runs perfect.

The shop worked on it for 1/2 day, not 1/2 hour before giving up and putting it to the back of the line. The first list is a combination of what I tried in and the shop guy tried. They still have the sled, it is 1 1/2 hours away, I am going to go get it in a few days.

The shop measured the fuel pressure at 59 psi, said that was right where it should be. That test result combined with the fact that it will run strong at 8000 rpm leads me to think that it isn't a fuel delivery problem to the injectors...if it is a fuel delivery issue that it would be post injector...it could be an injector that is not opening as it is supposed to do or it could be that it isn't getting the right firing signal at the problematic rpm range.

Your EGT suggestion has made me realize that I could attach a thermocouple to each exhaust manifold and monitor temperatures and if one cylider is not getting enough fuel at 7500 rpm it will be running lean and should hotter than the other. If it is getting fuel but not a spark it should be cooling down while bogging. I can do this on my stand in the garage...don't have to be blasting down the trail.
 

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Most troubles with any engine are found after extended storage. It makes is a lot easier to focus on the problems that are most likely to develop during this time period.

The SDI has two injectors per cylinder. One on the outer side of the engine that injects fuel up to a given rpm depending on the year, and the other that is used to share injector flow in the upper rpm range. If for example a problem develops at an rpm range that only one of the two injectors is working, than a problem with that one injector will have a large effect on air/fuel. In this same example at higher rpm when both injectors are working the effect of low flow of the low speed injector with be shared with the high speed injectors. Hence a flow problem with the low speed injector will be less significant at higher rpm as the flow is shared among two injectors.

Since the fuel pressure has been tested to be within tolerance, eliminating the possibility of a problem with the flow of injectors is the next step. You can ask the shop to perform a rudimentary flow test using BUDS, or you can bring the injectors to a shop for cleaning. If you do get the shop to remove the injectors for testing, please make 100% certain that each of the four injectors get identified prior to removal. It is very important to know which injector belonged to what position which is rarely done.

I will ask you one favour. On Monday morning I would like you to pick-up the phone and call any shop in North America that cleans injectors. You can provide your experience along with the explanation outlined in the second paragraph.
 

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Since the sled is already at the shop, it could be worth getting the injectors flow tested and bring them back to the shop for installation. This way you could develop a relationship with your shop to help with future work.

Remember you have no BUDS or CanDoo which is not playing in your favour. Personally I would rather spend the same money on getting well equipped to troubleshoot my own SDI sleds. At $75 an hour I can get 4 injectors cleaned or for double the money I can purchase the equipment to clean them myself. But I have a CanDoo and AFG to complete the tuning. It is all affordable. Take 4 hours at $75/hour, this adds up to $300. The sled is still not running and will take another 3 weeks plus another half of day or $300. This brings the amount of labour to $600. Add injector cleaning and this totals enough money to afford the equipment to perform the maintenance on multiple sleds.

After a half a day in the shop without it being solved and being told to wait another 3 weeks, it is a lot of trouble to be forking out that much money. Budget is everything with the older sleds.
 

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Maybe not similar but I had a summit 600sdi, that had dead spot between 7000-8000, ran awesome except for that and didn't do it all the time. I searched and a lot of poeple said to change the fuel filter under the handlebars. And also clutching, changing primary spring seemed to help a lot of guys. I'll check which spring guys were using.
 

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Discussion Starter · #10 ·
sorry it took so long to get back to this thread. In case anyone else gets here the problem was resolved with nothing more than fuel injector cleaner and a little time. A couple of weeks with a strong dose of injector cleaner in the system and the thing was rockin. Had a lot of rides since and even an off season and no problems at all this year.
 
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