Bike lacks power



  • Hi all I am not sure if I meant to introduce myself or not but I thought it would be for the best.

    I have a 2002 DTR and it lacks any real punch I know they aren't made to be seriously fast but even my friends DTRE is faster and from what I have heard they really are not all that quick, but my bike has many questionable things about it if I compare to what I have read online about my year I do believe it is a 3RMME it has the steering lock is not apart of the ignition.

    It has a 3mb barrel and the 3NB head I think it is I know that has the combustion disruption lip in it I think? but It has a full DEP system and a 240 main yet from what I can tell the bike is running pretty good fuel wise the plug is more like a biscuit brown if I do a plug chop the only thing I have not done is disconnecting a few wires from the black box in front of my two stroke tank.

    I do have some questions about the engine and was wondering if someone could offer me some better advice as this is my first two stroke so I still on the ropes about it all, from a visual check up the exhaust port the piston and barrel seem to have very minimal scoring on them, when I bought the bike I was told it was rebuilt at some point in the past not sure as of when.

    I know the squish gap is one of the main ways you make power out of a 2 stroke but how do you check it as I am not sure if when it was rebuilt someone may have set the squish wrong and maybe that is why it is down on power, I have already tried disconnecting the PV servo in hopes it was that but once the engine got to 7K and hit the powerband it still doesn't really have loads of go.

    and for example in second gear even at a slow speed if were to attempt a wheelie per say and you rev it up so the servo brings the powervalve fully open I presume and drop the clutch the bike will just try to die, it's like the bike is down on torque, but still has the horsepower maybe? as when 'racing' my friends DTRE both managed to run the bikes off the clock on the speedo but not sure how accurate they are.

    Any advice is appreciated thanks.



  • Hey there,

    Usually an introduction before asking questions is customary, especially if you're seeking help.

    2000-2004 DTR's are heavily restricted.

    Double check that all the destrictions have been done. The bike should fly along once done. Pulling hard to about 11k RPM. Sounds like your bike is restricted.

    Either grab yourself an aftermarket CDI unit. Or perform the destrictions. "Search" will be your friend here. It's all on this forum



  • @Calum Sorry about no introduction I wasn't sure where to introduce myself but I wasn't sure where to do so there is a good chance I just overlooked the new comers page.

    Do they make an aftermarket CDI for these bikes?



  • https://dt125r.co.uk/category/36/welcome-new-owners

    Yes. In my experience, aftermarket CDI was the single most impressive upgrade.



  • I mean, you shouldn't expect much.

    Please investigate what restrictions you still have on the bike, 99-03 should be clear to find, There are a few here.

    Big note, most of these production year DTRs are restricted to 8,000 RPM in the CDI, they have a heavier Generator design and the 3BN Cylinder head, you will only see under 20hp from these bikes fully de-restricted.

    Also big thing here is proper fuelling and sprocket sizes here, these are two things that explain alot of problems you may have,

    I maintain a servo DTR in standard form is the quicker bike, leave it on



  • @Darty According to the RPM tach on the bike it revs all the way round to roughly like 12K but the power falls off long before then it is pointless I have to shift at like 9.5k to keep it in the power.

    I was looking into having the resistrictor removed from the 3BN head if it was worth it or should I just buy a 3MB head?

    By any chance would you happen to know if I could fit a lighter generator on the bike?

    I do think the fueling is pretty ok the plug is more on the biscuit brown side but it is a tad rich.



  • Sounds like the powervalve to me. Or the reed switch. It should pull hard to the red line.

    Lightening the flywheel won't help.



  • @Ryan-F the 3mb head is ideal but hard to find since everyone wants them you can get your head de restricted if the powers dropping off like that I’d bet it’s the powervalve set set correctly



  • @Calum I did disconnected the servo and run it pinned fully open it was alot better and pulled all the way from rouhgly 7K to like 11K but I can't stand the lack of bottom end power after the powervalve is pinned.

    So I have reconnected it again and It's just not as quick up top from what I can tell I have set it up properly the diamond lines up with the hole and once you rev the bike onto powerband that is where the diamond moves too. Could it be the servo itself? it still makes the noise when you turn the igntion on.

    The reed switch is disconnected I left it behind the clocks though.



  • @declan they are a few ebay but they are quite pricey, was going to see if any shops near me would de-restrict it for me



  • @Ryan-F well you have your issue then it’s the powervalve yeah an engine porter should be able to do it no problem, the powervalve should whine as you turn the key if it doesn’t then there’s an issue the valve should be aligned through the exhaust port so that it’s a smooth transition as you look through the exhaust port there should be no step or ridge



  • @declan The issue being on the new models the powervalve retards after 8K RPM. Starving the engine of the power.

    Getting an older CDI unit, or an aftermarket one, would rectify this.



  • @Calum but it’s alreday revving freely so surely the cdi isn’t the issue I though if the cdi were restricted it would only rev to 9k like mine



  • The later CDIs control the powervalve servo. On crossers, the powervalve is controlled by the gearbox, or by exhaust pressure. On the DT it's controlled via the YPVS CDI. Early models this was separate from the CDI. Later models it was an all in one.



  • @Calum Is there a year roughly I would need to buy? and would I need a new loom or would it just be a case of wire it up and it's ready to go?



  • @declan Yeah the power valve works and wines as I turn the ignition I will have to look into what callum said about an old or aftermarket CDI, I was just scratching my head a little as it all seemed ok



  • @declan said in Bike lacks power:

    m

    It's like a 3RM model CDI. But to be honest, just get a Zeeltronic for it. It'll be better in the long run since it will be new, rather than buying something old and potentially faulty.

    https://www.thetuningworks.co.uk/store/product_info.php?products_id=1268

    £165



  • @Calum Ok thank you, do they come with like a base map at least?

    was looking at getting another top end and getting it ported also.



  • @Ryan-F Zeeltronic provide an array of maps that you can base yours on. They are more aggressive than the OEM maps. I've just left it as the one they provided. I altered the powervalve timings but that's about it IIRC. Best get the handheld programmer too. I found mine came with some crazy map that was totally inappropriate.



  • @Calum Ah ok thank you for the help, I was looking at the older CDI's but like you said alot of them look crusty and I know what you mean about the zeeltronic that is going to be my next buy 100% I don't want to make the bike crazy or nothing and i don't want mega horsepower I just like the torque and acceleration.


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