1.9DG Max speed issue

[Tommy D]

Hey guys ive just got my 86 hightop on the road after being stood since 2009.

It runs a 1.9DG and after looking about these should be good for 70mph atleast.

downhill i clocked it at 61mph MAX....

now i know its a nearly 9ft tall boat but surely it shouldnt be this limited???

when driving on the motorway it doesnt sound like the engine is sturggling... it just doesnt wind up to speed meaning im driving it with the throttle on the floor but im getting now where fast...

its runs and idles 10/10 though.

i gave it a service and have also ordered the derestriced rotr arm...

any advice would be appreciated.

also where is the location of the mixture screw???

Cheers Tommy

[CJH]

Slack in the accelerator cable perhaps? Take off the offside front indicator lens and see if it needs adjustment.

[Tommy D]

ill have a look cheers!

[Fully Loaded Cali']

Could be 2nd choke on the carb not opening up. My had the same issue, maxed out at 65 mph and no grunt up hills. Cleaned carb out and fitted new vacuum pipe, you can now feel the engine pick-up as the second choke comes in and will max out at 80 - 85 on the flat, empty and no bad head wind. (1984 Westy pop top 1.9DG).

[Tommy D]

So are they like a progressive unit like the webers?

[kevtherev]

unless you have a gas analyser don't touch the mixture screw.
That is for idle mixture only.
once you're at 1500 rpm your on the main jet anyway.

As well as the advice offered..

I would be having the carb off and cleaning it out.
I would be checking that the fuel pump is able to deliver fuel at higher speeds (pushrod is 100mm any less and it will begin to struggle)
I would be renewing the fuel filter.
I would be checking the advance on the timing, is it able to advance to 30 deg BTDC?
finally I would be renewing all the vacuum pipes, and checking for air leaks on the induction side.

[itchyfeet]

You say you serviced it but did you check the timing was set correctly with a timing gun and vacuum disconnected?

Many people overlook the timing and don't own a gun.
I had Atoomer23 round ths other day with his new van, he said if would not get up to speed, the timing was probably set with vacuum connected because it was way out but still idled and ran up to 60mph I think he said.

[batesy44]

Thaught that was normal tbh! My dg powered panel van did 59 at flat chat when I moved it to storage, mind u it was running like a bag of nails!
Now I have read this I will be setting the timing before I get her out for summer!

[itchyfeet]

Mg dg panel has been up to 80 on the clock ( probably 70 in the real world) and still has some beans left, takes a while to get there but if it's not climbing in speed on a flat road something is wrong.

[Aidan]

I would check to see which gearbox is fitted as it may have been previously swapped for a second hand box from a non turbo diesel - you'd expect to have a DU or ABD gearbox - if the box is correct then have the engine serviced/checked over - oh and the clutch isn't slipping a bit is it ?

[ajsimmo]

Aidan, surely if that were the case it'd take off like a dragster! Then be revving its nads off at top speed, but should still manage 70+ if you think about the revs (should happily pull 5k).
My money is on fuel/carb/timing, as above. Maybe centrifugal advance rusted stuck with standing so long?

[123-jn]

AT 70 mph mine is doing 3500 rpm just under and it's an auto gearbox which is very slightly lower geared in top due to final drive ratio. It will easily do 80 but I havent pushed it any further. (Dont show it a gradient though)

[ghost123uk]

Tommy, have you checked the two easiest (and not uncommon) issues as mentioned above by our esteemed contributors. That is, firstly, is full throttle at the pedal opening the carbs primary butterfly fully? A slack accelerator cable, as mentioned by CJH above, can prevent it opening fully. Ask me how I know Next, check the secondary butterfly valve is opening via it's black plastic vacuum diaphragm (as Fully Loaded Cali' mentions ^^^)

If those ain't the problem, proceed with the checks outlined by Kev ^^^ (and Itchyfeet etc of course)

Mine is a fairly lightly loaded Tin-Top camper with a very good nick DG in it. I run on Carat alloys with 205 full height tyres (not usual the lower profile 70's) so I have very slightly higher gearing (and love it). This makes my speedo damn near spot on (not the usual 10% fast). I have seen 85 on the speedo (and Sat Nav), on the level, with maybe a bit more to go, but didn't want to push it . Don't know what revs it is, but it didn't sound scary. I normally don't cruise at more than a "real" 70mph on my clock (which would read ~77mph on most folks speedos). It feels quite happy at that, but again, I do have slightly bigger tyres.

[kevinfromireland]

Tommy D, any progress made?

[Tommy D]

was the throttle cable