I put a MIkuni 45mm carb on my ds and it idles fine and runs fine at full throttle, but when your crusing and you punch it, it has a dead spot . We have changed the main jets and pilot jets up and down and its still the same. Any similar problems, or somebody want to take it off my hands?[img]i/expressions/face-icon-small-sad.gif[/img]

 

it's the nature of the beast. pm hightower he seems to really know his tm45. but if you don't have the pump active, hooking it up will help. other than that tell us what jets you are running. if you go fat on the main it will help some but you lose power. the thing is if you stay above 3500 it isn't a problem. you can also get in touch with ron woods racing they sell them and have info they will send lots of info.

 

To start to activate the pump, you'll need a Mikuni 50 pump jet to replace the 90 in the carb. You'll also need the pump parts from Ron Wood Racing. The rest of the activation is adjustment of the pump. Ron Wood has no idea what the pump adjustment is. I would suggest as Sandman says, contact Hightower on that.

 

I rode it around the yard today without the air filter and it ran fine. But if i put a smaller main jet i still have the same prob., Oh man the power is awesome, nothing to compare to the stock carb, if i could just get it tuned right

 

Its a wonderful carb, but has gotten a bad rep because nobody that sells them set them up right.
First off I have to say that this carb and most flat slide carbs are designed to work with an accelerator pump, and to not use the pump really does rob a guy of its true potential. I'd guess that yours is not set up to use the pump - either that or the pump is just not set up correctly.

When you hammer the throttle on a flatslilde carb, the massive rush of air from opening that gate so fast will stumble the engine - the pumper gives a squirt of fuel to fill this gap in time it takes for the syphon effect of fuel to catch up with theh airflow. When set up correctly, your front end will raise with a furious vengence like none you've experienced yet on your DS.

Before starting this venture, I highly suggest obtaining the Mikuni tuning manual for this carb - it is readily available from RWR and explains the function and troubleshooting of each of the 4 fuel circuits. This manual with help to better understand all the stuff I'm getting ready to write below, and also has a great parts diagram for you to order anything that may be missing.

Because of the lack of understanding of the accelerator pump on this carb, all too many people choose to run without it and just live with the bogging coming off idle. There are 3 accel pump nozzles - 50,60,70 - and the carb comes stock with a 70 which is too big for the DS. You need the 50. They are like $3 from Ron Wood Racing. And those that sell this carb without the pump working typically install pilots that are really too big, to try and make up for the lack of the pumper. So before tuning your pump you must first tune the pilot circuit correctly. The Mikuni tuning manual instructions are super and walk you thru the pilot jet/idle mixture adjustment very easily. You will most likely need a pilot somewhere between 20 and 30, depending on how you airbox is arranged, i.e. carb mount filter, no lid, etc.

Using the pumper adds stiffness to the throttle - this carb was designed to use a twist throttle so if you wanna use the thumg throttle then spring mods will need to be done. See a post I had a while back on TM45 made easy for thumb throttle, or something like that.
If this is something you wanna get into messing with, let me know and I'll help. if you wanna sell the carb, let me know 'cause I want a second one to set up for Alky on my bike!

 

Once the pump rod is put into place, there are only two screws used to adjust the squirt. My old mechanic was doing 4-5 carbs a week, but decided to stop for some reason. Anyways, thats the whole secret with the pump, is setting the screws in or out. Altitude does not matter. The adjustment works for everyone, with a rotax motor (stock bore).

 

I would like to keep it because the power is awesome, butr i dont know alot about carbs so any help is appreciated

 

porbably should call woods and get the manual first then you will know enough and what you don't someone on here will be able to help.

 

You can also download the manual from mikuni's site...